Issued  March  9,  1907. 


=jj§:       U.  S.  DEPARTMENT  OF  AGRICULTURE, 

~.  BUREAU  OF  ANIMAL  INDUSTRY.— Rui.letin  No    94. 

ZIZZZ  A     1)     MK1  V1N.    Chirk  M   Bwi 


IVEST1GATI0NS  IN  THE  USE  OF  THE 
'       BOMB  CALORIMETER. 


IN  COOPERATION  WITH  THE  PENNSYLVANIA  STATE 
COLLEGE   AGRICULTURAL   EXPERIMENT  STATION. 


BY 


J.   AUGUST   FRIES,   M.  S.. 


A  ft 


•fssistant  Expert  in  .Animal  X til  tit  ion . 


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WASHINGTON: 

GOVERNMENT   PRINTING   OHHCH 

1907. 


^ 


Property  of  the  United  States  Government. 

Issued  Mnrch  9,  1907. 

U.  S.  DEPARTMENT  OF  AGRICULTURE, 

BUREAU  OF  ANIMAL  INDUSTRY.— Bulletin  No.  94. 
A.  D.  MELVIN,  Chief  of  Bureau. 


INVESTIGATIONS  IN  THE  USE  OF  THE 
BOMB  CALORIMETER. 


IN  COOPERATION  WITH  THE   PENNSYLVANIA  STATE 
COLLEGE  AGRICULTURAL  EXPERIMENT  STATION. 


BY 


J.  AUGUST  FRIES,  M.  S„« 

Assistant  Expert  in  Animal  Nutrition. 


WASHINGTON: 

GOVERNMENT    PRINTING   OFFICE. 

1907. 


BUREAU  OF  ANIMAL  INDUSTRY. 


Chief:  A.  D.  Melyin. 

Assistant  Chief:  A.  M.  Farrington. 

Chief  Clerk:  E.  B.  Jones. 

Biochemic  Division:  Marion  Dorset,  chief;  James  A.  Emery,  assistant  chief. 

Dairy  Division:  Ed.  H.  Webster,  chief;  C.  B.  Lane,  assistant  chief. 

Inspection  Division:  Rice  P.  Steddom,  chief;  U.  G.  Houck,  associate  chief;  Morris 
Wooden,  assistant  chief. 

Pathological  Division:  John  R.  Mohler,  chief;  Henry  J.  Washburn,  assistant 
chief. 

Quarantine  Division:  Richard  W.  Hickman,  chief. 

Division  of  Zoology:  Brayton  H.  Ransom,  chief. 

Experiment  Station:  E.  C.  Schroeder,  superintendent;  W.  E.  Cotton,  assistant. 

Editor:  James  M.  Pickens. 

ANIMAL    HUSBANDRY    OFFICE. 

.[•I in inistrative  Staff. 

Animal  Husbandman:  George  M.  Rommel. 
Assistant  Aui null  Husbandman:  G.  Arthur  Bell. 

Animal  breeding  investigations:  Animal  Husbandman,  in  charge;  E.  H.  Riley,  scien- 
tific assistant. 
Supervision  of  pedigree  record  associations:  George  R.  Samson,  herdbook  assistant. 
Poultry  investigations;  Rob  R.  Slocum,  poultry  assistant. 
Hog  investigations:  L.  R.  Davies,  scientific  assistant. 

Cooperative  staff. 

Animal  nutrition  investigations:  H.  P.  Arinsbv,  expert  in  charge;  J.  August  Fries, 
W.  \V.  Bremen,  F.  \V.  Christensen,  assistants. 

/;,./'  production  in  the  South:  I).  T.  <iray,  expert  in  charge;  W.  F.  Ward,  assistant. 

Horse  breeding  investigations:  \V.  L.  Carlyle,  expert  in  charge  of  Colorado  work; 
\V.  F.  Ilainiii 1,  expert  in  charge  of  Vermont  work. 

Poultry  breeding  investigations:  Gilbert  M.  Govvell,  expert  in  charge. 

Slieep  breeding  investigations:  George  F.  Morton,  expert  in  charge. 

Turkey  breeding  i a nxt igal inns:  Leon  J.  Cole,  expert  in  charge;  W.  F.  Kirkpatrick, 
assistant. 
2 


LETTER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Bureau  of  Animal  Industry, 
Washington,  D.  C. ,  December  15,  1906. 
Sir:  I  have  the  honor  to  transmit  herewith,  and  to  recommend  for 
publication   as  a    bulletin    of    this    Bureau,  a  manuscript    entitled 
"Investigations  in  the  Use  of  the  Bomb  Calorimeter,"  by  J.  August 
Fries,  M.  S.,  assistant  expert  in  animal  nutrition.     The  experiments 
described  in  this  article  a*e  a  part  of  the  investigations  in  animal 
nutrition  conducted  at  the  Pennsylvania  State  Agricultural  Experi- 
ment Station  by  cooperation  between  that  station  and  this  Bureau. 
The  particular  objects  and  value  of  the  work  reported  bj'  Mr.  Fries 
are  described  in  the  accompanying  letter  by  Doctor  Armsby,  the 
expert  in  charge  of  the  cooperative  investigations. 
Respectfully, 

A.  D.  Melvin,  Chief  of  Bureau. 
Hon.  James  Wilson, 

Secretary  of  Agriculture. 

3 


LETTER  OF  SUBMITTAL. 


State  College,  Pa.,  October  18,  1906. 

Sir:  The  investigations  upon  the  energy  values  of  feeding  stuffs 
which  are  being  carried  on,  with  the  aid  of  the  respiration  calorimeter, 
in  cooperation  with  the  Pennsylvania  Experiment  Station,  depend  in 
large  part  for  their  value  upon  accurate  determinations  of  the  heats  of 
combustion  of  the  feeds  and  of  the  visible  excreta.  The  bomb  calo- 
rimeter of  Berthelot  in  its  various  modifications  is  recognized  as  the 
most  convenient  and  accurate  instrument  for  this  purpose  which  has 
thus  far  been  devised,  and  the  modification  of  it  known  as  the  Atwater- 
Hempel  bomb  has  been  used  in  these  investigations.  Since  the  values 
obtained  with  this  instrument  are  fundamental  to  the  research,  it  is 
obvious  that  critical  study  should  be  given  to  the  accuracy  of  the 
method  employed. 

I  have  the  honor  to  submit  herewith  the  results  of  experiments  by 
Mr.  J.  August  Fries,  assistant  expert  in  animal  nutrition,  upon  this 
subject.  These  experiments  have  been  made  during  the  past  four 
years  in  connection  with  the  investigations  in  animal  nutrition  reported 
or  in  progress,  and  their  results  indicate  some  of  the  possible  sources 
of  error  in  the  method  and  the  precautions  necessary  in  its  use  to 
secure  accuracy,  while  they  also  show  the  need  of  further  experiments 
on  the  same  subject.  It  is  hoped  that  these  results  may  be  of  value  to 
other  investigators  in  the  same  field. 
Very  respectfully, 

Henry  Prentiss  Armsby, 
Expert  in  Animal  Nutrition. 

Dr.  A.  D.  Melvin, 

(  h  i<f  of  the  Bureau  of  Animal  Industry. 
4 


CONTENTS. 


Page. 

Introductory ,. 7 

The  apparatus  used 7 

Manipulation  of  the  apparatus 7 

Calculation  of  results 8 

Importance  of  the  apparatus  in  calorinietric  determinations 10 

Earlier  determinations  of  heats  of  combustion 10 

Variations  in  determinations  already  on  record 17 

Causes  of  differences  in  heat  determinations 18 

Impure  oxygen ;.  19 

Testing  of  oxygen 19 

Correction  for  impurity  in  the  oxygen 22 

Rise  in  temperature  corrected  for  heat  due  to  impurities  in  the  oxygen .  26 

Formation  of  nitric  acid  in  the  bomb  calorimeter  during  combustion 27 

Oxidation  of  combined  nitrogen  to  nitric  acid 28 

Probable  error  due  to  disappearance  of  nitric  acid 31 

Cause  of  incomplete  combustion 33 

Alcohol  heat  value 35 

Alcohol  determination  used  for  testing  the  respiration  calorimeter 36 

Determination  of  heat  of  combustion 36 

Conclusion , 38 

5 


Digitized  by  the  Internet  Archive 

in  2007  with  funding  from 

Microsoft  Corporation 


http://www.archive.org/details/bombcalorOOfrieiala 


INVESTIGATIONS  IN  THE  USE  OF  THE  BOMB 
CALORIMETER. 


INTRODUCTORY. 

In  scientific  investigations,  us  well  as  in  technical  work,  it  is  often 
of  very  great  importance  to  know  the  exact  heat  of  combustion,  or,  in 
other  words,  the  energy  value  of  a  substance.  To  determine  the  heats 
of  combustion  of  organic  compounds  it  is  necessary  to  completely  oxi- 
dize them  to  their  most  simple  or  stable  decomposition  products  and 
measure  the  heat  evolved.  Several  methods  have  been  used  for  such 
determinations,  but  the  latest  and  best  for  the  greater  number  of  com- 
pounds is  undoubtedly  the  Berthelot  or  bomb-calorimeter  method, 
where  the  substance  to  be  anal\Tzed  is  burned  in  oxygen  gas  under 
high  pressure.  Detailed  descriptions  of  this  apparatus  and  directions 
for  its  use  are  found  in  various  scientific  works,  hence  no  full  descrip- 
tion need  be  given  here. 

THE  APPARATUS  USED. 

The  apparatus  used  for  the  work  described  in  this  paper  was  the 
Atwater-Hempel  bomb  calorimeter,  which  is  a  modification  of  the  Ber- 
thelot apparatus."  The  main  features  only  of  its  construction  and 
manipulation  will  be  referred  to  briefly  at  this  time. 

The  apparatus  consists  of  the  bomb  proper,  which  is  a  strong  steel 
cup  lined  on  the  inside  with  platinum,  and  of  a  platinum-lined  top 
which  rests  on  a  lead  washer  and  is  firmly  held  in  place  bjT  a  threaded 
collar.  A  cylindrical  vessel  of  Britannia  metal  is  used  for  holding  the 
water  in  which  the  bomb  is  immersed.  The  apparatus  is  provided 
with  a  stirring  arrangement  operated  by  means  of  an  electric  motor. 
Outside  of  this  metal  vessel  are  two  concentric  protecting  cylinders 
made  of  indurated  fiber,  each  provided  with  a  cover.  These  fiber 
cylinders,  with  the  dead  air  spaces  between  them,  serve  to  insulate 
and  protect  the  metal  vessel  and  the  water  as  far  as  possible  from 
being  affected  by  any  change  of  outside  or  room  temperature  or  circu- 
lation of  air.  A  Beekmann  mercury  thermometer,  which  can  be  read 
to  0.001°  C.  with  accuracy,  is  used  for  taking  the  temperatuie  of 
the  water. 

MAMITI.ATION    OF   T1IK    APPARATUS. 

The  substance  to  be  burned,  if  solid,  is  pressed  into  a  tablet  of  con- 
venient size,  placed  in  a  platinum  capsule,  which  is  supported  on  a 

oTJ.  S.  Dept.  Agr.,  Office  of  Experiment  Stations  Bui.  21.  Conn  (Storre)  Sta. 
Kept.,  1897,  p.  199. 


8  INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 

platinum  wire  attached  to  the  top  or  cover  of  thebomb,  and  adjusted 
so  that  the  substance  will  come  in  contact  with  the  fine  iron  fuse  wire  by 
means  of  which  it  is  ignited.  The  bomb  is  then  charged  with  oxygen  gas 
to  a  pressure  of  at  least  20  atmospheres.  It  is  immersed  in  the  weighed 
quantity  of  water,  the  electric  connections  are  made,  and  the  covers 
adjusted  and  clamped  so  that  the  stirrer  will  not  rub.  After  placing  the 
thermometer  in  position  the  stirrer  is  started  and  the  temperature  of  the 
water  taken.  It  is  intended  to  have  the  water  as  much  colder  than  the 
surrounding  air  before  the  combustion  as  it  will  be  warmer  after  the 
combustion.  As  soon  as  a  uniform  rate  of  change  in  the  water  tempera- 
ture has  been  established  the  substance  is  ignited.  For  this  purpose  an 
electric  current  strong  enough  to  fuse  instantly  the  fine  iron  wire  is 
allowed  to  pass  through ,  and  by  the  burning  of  the  fuse  wire  the  substance 
in  the  capsule  is  also  instantty  ignited.  The  combustion  is  only  of  a  few 
seconds'  duration,  and  the  heat  formed  is  quickly  transmitted  through 
the  bomb  to  the  surrounding  water.  Readings  of  the  thermometer 
are  taken  every  minute,  and  from  the  rise  in  temperature  of  the  water 
the  heat  generated  is  calculated. 

CALCULATION   OF   RESULTS. 

In  the  calculation  of  the  results  it  is  necessary  to  apply  several  cor- 
rections. Not  only  the  fixed  weighed  quantity  of  water  but  the  whole 
system — bomb,  stirrer,  metal  vessel,  etc. — is  heated  up  to  the  same 
degree,  therefore  the  correct  thermoequivalent  of  it  must  be  deter- 
mined and  used.  Thermometer  readings  must  be  corrected  according 
to  the  individual  thermometer  used.  Corrections  are  also  made  for 
the  influence  of  the  surrounding  air  temperature,  the  heat  generated 
by  the  burning  of  the  fuse  wire,  the  formation  of  nitric  acid  in  the 
bomb,  and  the  lag  of  the  thermometer. 

The  formula  which  has  been  used  in  working  out  the  correction  for 
the  outside  air  influences  is  the  Kegnault-Pfaundler  formula,  given  in 
Wiley's  Principles  and  Practice  of  Agricultural  Analysis,  Volume  III, 
page  572,  and  the  following  example  will  serve  to  illustrate  the  main 
points  to  In-  observed  in  connection  with  the  determination  and  calcu- 
lation of  the  heat  of  combustion. 

Formula: 


ti-t\  i  ' 


+BjiY^-nt)-(n-l)*=2/lt. 


n  fi  —6 

2  0,     Hum  of  ()  reading*  minus  1  increased  bv  an  arbitrary  factor   -      U 

1  y 

r  =  average  rate  of  radiation  during  preliminary  period. 
»■'  = average  rate  of  radiation  during  end  period, 
0  =  number  of  reading!  during  combustion  period. 
f  =  average  «>f  preliminary  thermometer  readings. 
0  =  average  <>f  end  period  thermometer  readings. 


CALCULATION    OF    RESULTS. 

Example:  Cellulose. 

Cellulose,  dried  at  105°  C.  1.0035  gram. 

Iron  fuse  wire  0.0118  -  -  0.0018  =  0.0100  gram  =  16  calories. 

Oxygen  pressure  =  24  atmospheres. 

Room  temperature,  21°  C. 

Water  temperature,  19°  C.  at  beginning. 

HN03  titrated  =  13.5  e.  c.  NaOH  sol.  =  13.5  calories. 

Cellulose  ignited  instantly. 

Thermometer  readings  begin,  1.220,     1.220,     1.220,     1.221,     1.221,     1.221. 
Corrected  readings  begin,         1.2265,  1.2265,  1.2265,  1.2275,  1.2275,  1.2275. 

Combustion  period,  1.221,     2.630,     2.933,     2.952,     2.952. 

Corrected  readings,  1.2275,  2.6414,  2.9450,  2.9640,  2.9640. 

End  period,  2.952,     2.949,     2.945,     2.941,     2.937. 

Corrected  reading,  2.9640,  2.9610,  2.9570,  2.9530,  2.9490. 

v  =  0.0002. 
t  =  1.2270. 
6  =  5. 
vl  =  -  0.0038. 
^  =  2.9565. 

0  0002 ( 0  0038^/"  "\ 

'2  9565-1  2270   \  9.9350 +  2.0958 -6. 1350 J— 0.0008=  +0.013°. 

2  A  t=  +0.013°. 

Last  reading  of  combustion  period,  +  2.9640°  C. 

First  reading  of  combustion  period,  —  1.2275°  C. 

Correction  for  outside  air,  +  0.0130°  C. 

Correction  for  thermometer  lag,  —  0.0006°  C. 


1.7489°  C. 

Correction  for  excess  oxygen,  +  0. 0003°  C. 
Correction  for  impurities  in  oxygen,—  0.  0151°  C. 

Corrected  rise  in  temperature,  +  1.  7341°  0. 

Water  value  of  bomb  system  with  20 

atmospheres  (2, 439.  2)  X  rise  =  4229.  82  calories. 

Correction  tor  fuse  wire,  —     16.  00  calories. 

Correction  for  HNO„  —     13. 50  calories. 


4229. 32  calories. 
4229.32  -^-  1. 0035  =  4185.  7  calories  per  gram  of  cellulose. 

Should  for  some  reason  the  current  of  electricity  remain  on  for  a 
few  seconds  before  the  wire  fuses,  correction  should  be  made  for  the 
heat  generated  by  the  current. 
18399— No.  94—07 2 


10  INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 

IMPORTANCE    OF    THE    APPARATUS    IN    CALORIMETRIC   DETER- 
MINATIONS. 

Not  only  in  physical  and  chemical  laboratories  do  calorimetric  deter- 
minations find  application,  but  they  have  acquired  special  prominence 
in  connection  with  physiological  investigations  and  research  work,  and 
it  is  in  this  line  of  work  that  at  the  present  time  their  application  in 
the  agricultural  science  has  been  found  to  be  of  so  great  importance. 
Thus,  the  very  elaborate,  time-consuming,  and  expensive  nutrition 
investigation  experiments  with  cattle  by  the  use  of  the  respiration 
calorimeter  are  so  planned  that  the  successful  solving  of  the  question 
of  energy  metabolism  in  the  animal  body  rests  almost  entirely  upon 
the  bomb  calorimeter — upon  its  efficiency  in  quickly  and  accurately 
determining  the  heats  of  combustion  of  feed  and  excreta.  Being, 
then,  a  most  important  part  of  the  whole  plan,  and  since  so  much 
depends  upon  the  work  of  this  apparatus,  one  is  not  justified,  because 
much  work  has  been  done  with  it  in  the  past,  in  assuming  that  it  is 
perfect  in  all  respects,  or  that  it  is  adapted  alike  to  all  kinds  of  organic 
substances.  Instead,  it  should  be  severely  tested  from  different  points 
of  view,  and  that  was  the  object  of  this  work. 

EARLIER  DETERMINATIONS  OF  HEATS  OF  COMBUSTION. 

To  begin  with,  it  may  be  well  to  look  a  little  into  the  work  already 
done,  and  note  the  condition  in  which  our  knowledge  of  the  heat  values 
of  organic  substances  is  at  the  present  time,  and  how  well  different 
investigators  agree  in  their  determinations.  For  this  purpose,  as  well 
as  to  get  a  general  idea  of  heat  values,  I  have,  without  going  back  to 
the  original  source  of  the  information,  collected  and  tabulated  a  large 
number  of  results  upon  the  heats  of  combustion  of  the  more  common 
organic  substances  as  obtained  by  various  investigators.  The  values 
are  taken  from  text-books  and  scientific  reference  books,  some  of  which 
are  still  in  use  in  schools  and  elsewhere. 

To  make  the  tables  as  condensed  as  possible  the  works  or  books 
referred  to  are  represented  in  one  column,  each  book  by  a  single  num- 
ber, and  the  investigators  in  another  column  by  the  first  letters  of 
their  respective  names. 


EARLIER    DETERMINATIONS. 


11 


Table  I. — Heats  of  combustion  of  1-gram  substance,  expressed  in  small  calories. 


Substance. 


ELEMENTS,    ETC. 

Hydrogen 

Hydrogen  (8  investigators) 

Do 

Carbon 

Charcoal  (wood ) 

Charcoal  (sugar) 

Do 

Do 

Diamond  (toC02) 

Diamond  (to  CO) 

Iron  (to  Fe.,0;i) 

Iron  (to  Feb) 

Sulphur 

Do 

Sulphur  (soft) 

Do 

CO  to  CO. 

Do  ..." 

Do 

Do 

Do 

Nitrogen  to  HN03  (sol.) 

NOtoN02 


Formula. 


PROTEIDS,  ETC.  (ALBUMINOIDS.) 


Gluten 

Do 

Elastin 

Plant  fibrin 

Do 

Do 

Serum  albumin 

Syntonin 

Hemoglobin  ... 

Do 

Do 

Do 

Do 

Milk  casein 

Do 


Do 

Do 

Do 

Do 

Do 

Do 

Yolk  of  egg 

Yolk  of  egg  (fat  free) . 
Legumin 

Do 

Vitellin 

Do 

Do 


II.", . 
\C. 

c. 
c. 
c. 
c. 
c. 
c. 

0... 

We . 

Fc. 

§».. 

s.",.. 

8*.. 


Refer- 

Investiga- 

ences, a 

tors,  a 

34, 462. 0 

1,3 

F.&S. 

34, 154. 3 

'10 

F.&S. 

34, 800. 0 

10 

H. 

7, 770. 1 

10 

F.&S. 

S,  080. 0 

1, 3, 10 

F.&S. 

7,714.0 

10 

Gr. 

8, 039. 8 

10 

F.&S. 

7, 965. 0 

10 

Sch. 

7, 859. 0 

10 

B.&P. 

2,141.7 

10 

B. 

1, 600. 0 

9 

1,352.6 

10 

F.&S. 

2,260.3 

10 

F.&S. 

2, 165. 6 

10 

B. 

2, 220. 5 

10 

F.&S. 

2, 162. 5 

3 

F.&S. 

2,436.0 

3 

F.&S. 

2, 431. 0 

10 

An. 

2, 402. 7 

10 

F.&S. 

2,438.6 

10 

B. 

2,441.7 

10 

Th. 

1,022.6 

8 

652.3 

10 

Th. 

5-,  990. 3 

2 

B. 

6, 141. 0 

2 

D. 

5,961.3 

1,2,10 

St.&L. 

5, 832. 3 

2,10 

B.&A. 

5,941.6 

2,10 

St.  &  L. 

6,231.0 

1.2 

D. 

5, 917. 8 

1,2,8,10 

St.&L. 

5, 907. 8 

2,1 

St.  &  L. 

5,910.0 

2,10 

B.&A. 

5, 914. 8 

1,3 

B.&A. 

5,885.1 

1,2,3,10 

St.&L. 

5, 950. 0 

2 

Ru. 

5,949.0 

1,2,3,10 

D. 

5, 626. 4 

2,10 

B.&A. 

5, 867. 0 

2,3,8,10 

St.  &  L. 

5, 629. 2 

1,3 

B.&A. 

5,717.0 

1,2,3,10 

St. 

5, 785. 0 

2 

D. 

5, 849.  6 

2,3,10 

St.  &  L. 

5, 858. 0 

1 

St.&L. 

5, 855. 0 

1 

D. 

8,112.4 

2,3. 

B.&A. 

5, 840. 9 

3,10 

St.  &  L. 

5, 793. 1 

1,2,10 

St.  &  L. 

5, 573.  0 

2 

D. 

5, 780.  6 

2,10 

B.&A. 

5, 745. 1 

1.2,3,10 

St.&L. 

5, 784. 1 

3 

St.  &  L. 

1. 

2. 

3. 

4. 
5. 
6. 
7. 
8. 
9. 
10. 

A. 

An 

B. 

Hi! 

I) 

1)11 

F. 

F<>. 
Ft. 
<;i. 
So. 


Abbreviations: 

Works  referred  to— 
Bunge,  Physiological  Chemistry,  fourth  German  edition,  1902. 
Armsby,  Principles  of  Animal  Nutrition,  1904,  and  U.  S.  Department  of  Agriculture,  Office  of 

Experiment  Stations,  Bulletin  21. 
Beilage,  Ohemiker  Kalender,  1904. 
Tollen,  Handbuch  I  der  Kohlehydrate,  1898. 

W.  Ostvvald.  Grundriss  der  Allgemeinen  Chemie,  2te  Auflage,  1890. 
Tollen,  Handbuch  II  der  Kohlehydrate,  1895. 
Jones,  Elements  of  Physical  Chemistry,  1903. 

Wiley.  Principles  and  Practice  of  Agricultural  Analysis,  Vol.  Ill,  1897. 
Journal  American  Chemical  Society,  Vol.  XXV,  1903. 
Landolt  &  Bcimstein,  Physikalisch-Chemische  Tabellen,  1894. 
Investigators — 

Andre.  Gr.   Grassi. 

.  Andrews.  H.     Hess. 

Berthelot.  He.  Herzberg. 

,  Bunson.  J.      Jahn. 

Danilewsky.  K.     Kleber. 

.  Dulong.  L.      Langbein. 

Favre.  Lu.  Luginni. 

Fogh.  M.    Matignon. 

Frankland.  O.     Ogier. 

Gibson.      -  P.    Petit. 

Gottlieb. 

b  Lowest.  c  Highest. 


Rch 

Rechenberg. 

Re. 

Recoura. 

Ro. 

Rodolz. 

Ru. 

Rubner. 

8. 

Silbermann. 

Sch. 

Scb.waokb.5fei 

St. 

Stohmann. 

T. 

Tower. 

Th. 

Thomson. 

V. 

Vieille. 

12 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


Table  I. — Heeds  of  combustion  of  1-gram  substance,  expressed  in  small  calories — Cont'd. 


Substance. 


Formula. 


Refer- 

Investiga- 

ences. 

tors. 

5, 687. 4 

1,2,10 

B.&A. 

5, 735. 2 

1,2,3,8,10 

St.  &  L. 

5,579.0 

1,2,3,10 

St. 

5, 690. 6 

3 

St. 

5, 728. 4 

2,10 

B.&A. 

5, 720. 5 

2, 8, 10 

St.  &  L. 

5, 662. 6 

2,10 

St.  &  L. 

5, 324. 0 

2,10 

St. 

5,656.0 

2,10 

Ru. 

5, 640. 9 

2,10 

St.&L. 

5,345.0 

10 

Ru. 

5,672.0 

1,2,10 

St.&L. 

5,598.0 

1,2,10 

St. 

5, 529. 1 

2,10 

B.&A. 

5, 637. 1 

2, 3, 10 

St.  &  L. 

5, 511. 0 

1,2,3,10 

St. 

5, 709. 0 

2 

D. 

5, 772. 0 

1 

D. 

5,532.4 

.      3 

St. 

5, 567. 3 

3 

St. 

5, 553. 0 

2 

St.&  L. 

5,564.2 

2 

B.&A. 

5, 510. 2 

2 

St.  &  L. 

5,479.0 

2,10 

St.  &  L. 

5, 362. 0 

2,10 

St. 

5,355.1 

2,10 

St.  &  L. 

5, 298. 8 

1,2,3,8,10 

St.  &  L. 

5, 069. 0 

2 

D. 

4, 876. 0 

1 

D. 

4, 914. 0 

1 

D. 

5, 240. 1 

2,10 

B.&A. 

6, 493. 0 

1,2 

D. 

5, 342. 4 

1.2,3,10 

B.&A. 

5,130.6 

1,2,3,10 

St.  &  L. 

4,909.0 

2 

D. 

5, 410. 4 

1,2,10 

B.&A. 

5,039.9 

1,2,10 

St.  &  L. 

5,095.7 

2,10 

St.  &  L. 

4,979.6 

2,10 

St.  &  L. 

4,655.0 

2,10 

St.  &  L. 

4,650.3 

2,10 

B.  &  A. 

4,146.8 

2,10 

B.&A. 

5,637.0 

1,2,10 

St. 

5,793.0 

1,10 

St.  &  L. 

5, 730. 8 

8 

2, 530. 1 

2,10 

B.  .V  I'. 

2,541.9 

1,2,10 

St.  &  L. 

2, 465. 0 

1,2,5,10 

St. 

2,537.0 

1.2 

D. 

2, 638,  o 

2,10 

R. 

2,121.0 

1 

K. 

3,133.6 

2,9,10 

B.  &  A. 

3, 129. 1 

2,9,10 

St.  &  L. 

3,050.0 

1 

St. 

3,053.0 

2,10 

St. 

4,370.7 

2,10 

B.&A. 

4,355.5 

2,10 

St.  &  L. 

6,536.5 

1,2,10 

It.  A   A 

6,525.1 

1,3,10 

St.  &  L. 

4,505.9 

1,2,10 

st.  &  L 

5,659.3 

1,2,9,10 

li.  A     \. 

5,668.2 

1,2,9,10 

St.  &  L. 

5,642.0 

2,5,10 

St. 

2,911.1 

2,10 

B.&A. 

3,423.0 

1 

St. 

2,899.0 

2,10 

SI.  A:  L 

5,915.9 

1,2.  10 

B,  A  A. 

8,896.  8 

2,10 

I!    A    \. 

3,514.0 

2,10 

St.  &  L. 

3,428.0 

2,10 

St. 

3,714.1 

1.2.10 

Bt,  a  L 

4,275.4 

1,2,10 

SI.  A  L 

(8,306.0) 

2 

1). 

2,754.0 

2,10 

B,  &  M. 

2,749.9 

1,2,10 

St.  &  L. 

2,(121.0 

1,2,5,10 

SI. 

2,646.0 

1 

Fr. 

PROTEIDS,  ETC.  (  ALBUMINOIDS) — COn. 


Egg  albumin 

Do 

Do 

Do 

Muscle  (fat  free  and  water) . 

Muscle  ( extracted) 

Muscle  (fat  free) 

Do 

Muscle  (fat  free,  ash  free)  . . 

Do 

Do 

Albumin  cryst 

Do 

Blood  fibrin 

Do 

Do 

Do 

Do 

Do 

Do 

Albumin  (Harnack's) 

Wool 

Do 

Congluten 

Do 

Fibrin  of  skin 

Peptone 

Do 

Do 

Do 

Fish  glue 

Do 

Chondrin 

Do 

Do 

Ossein 

Do 

Fibroin  

Do 

Chitin 

Do 

Tunicin 

Paraglobulin ; 

Legumin 

Proteids  (mean)  


AMIDES,  KT<\ 


Urea 

Do 

Do 

Do 

D-. 

Do 

Qlyoocoll 

Do 

Do 

Do 

Alanin 

Do 

Leucin 

Do 

Sarkosin 

Hippuric  acid 

Do  .'.'.'.'.'.'.'.W.'.'. 

A-pnrlir  acid 

Do 

Do 

Tynwin , 

Amanurla 

i«, 

Do 

Croatia  erytt , 

Croatia,  ftnbrdrooa 

Do 

I'rii-  acid 

Do 

i". 

Do 


CON2H4 

con,h4   

CON2H4 

CON2H4 

CON2H4 

CON,H4 

CrL/foO. 

<:h.no2 

C2H5N02 

C,H6NO, 

<;II7N02 , 

C3H,N02 

GtHuNQi 

CHuNO,.,.. 

C.,H7N02 

«,I1,,N03 

CoHoNOg 

C,H,NOa 

C4H7N04 

C4H7NO4 

clHjNOj 

Ci,HuNO, 

C4H„Vi20, 

C4IKN.  <   I 

<'(M.N.,0, 

.  .11  \  0..11.0. 
•    ii  v;o2 


<'.-,H,N4(>, 
C»H4N40,. 

C.-,H4N40:1. 
Cr,H4N,0:l. 


EARLIER    DETERMINATIONS.  13 

Table  I. — HeaU  of  combustion  of  1-gram  substance,  expressed  in  small  calories — Cont'd. 


Substance. 


amides,  etc. — continued. 


Guanin  .. 
Guanidin 
Caffein . . . 


FATS (ANIMAL' 


Fat  of  swine 

Do 

Do 

Do 

Do 

Fats  of  oxen 

Do 

Do 

Do 

Fats  of  sheep  

Do 

Do 

Fat  of  horse 

Fat  of  dog 

Fat  of  goose 

Fat  of  duck 

Fat  of  man 

Sperm  oil 

Butter  fat 

Do 

Do ... 

Do 

Do 

Do 

Fat,  mean  (man,  oxen,  sheep) 

Fat,  mean  (dog,  swine) 

Fat,  mean  (goose,  duck) 

Do 


FATS  (VEGETABLE). 


Olive  oil  (expressed) . 
Do 


Do 
Do 
Do 
Do 


Do 

Poppy-seed  oil 
Rape-seed  oil  . 

Do 


Do 


Ether  extract— Various  seeds. 

CARBOHYDRATES,  ETC. 


Arabinose 

Do 

Do 

Xylose 

Do 

Fucose 

Rhamnose  (water  free) .. 
Rhamnose  (crystallized). 

Sorbinose 

Galactose 

Do 

Dextrose  (glucose), 

Do 

Do 

Do 

Do 

Do 

Dextrose  (hydrated) 

LevHlose  (fructose) 

Glucoheptose 

Cane  suga  r  ( sucrose ) 

Do 


Do 
Do 
Do 
Do 
Do 


Formula. 


C5H5N5O. 
CH5N3.... 

C8H,0N4O, 


Calories. 


C5H10O5 

C.iHjoO;, 

C5H10O5 

Q-.HjoO; 

CsH^Cv, 

C«Hi20--, 

( Y.HioOf, 

C0H,..0, 1 1,«). 

CoH120« 

CcH]2Oc 

(V.H12OV, 

CoH]oOo 

(Y,H12Og 

(V,Hi.)Oo 

CgHijQg 

CoHijOo 

CsHnOt 

(V)H,.,0„ll.(>. 

(V.HlnOo 

CtHhO; 

Cl2H.»On 

CjoH.wO], 

(;i2HooO;, 

CmHmOu — 

('12H020II 

C12H02011 . . . . 

cloHOJOll  — 


3,891.7 
4, 197. 0 
5,231.4 


9, 476. 9 
9,380.0 
9,686.0 
9,423.0 
9,515.0 

9. 485. 7 
9, 357. 0 
9,427.0 
9, 686. 0 
9, 493. 6 
9, 406. 0 
9,530.0 
9, 410. 0 
9, 330. 0 
9,345.0 
9,324.0 
9, 398. 0 

10,001.0 

9. 215. 8 
9, 192. 0 
9,185.0 
9,231.3 
9, 179. 0 
9,230.0 
9, 365. 0 
9,423.0 
9,500.0 
9, 372. 0 


9, 328. 0 
9,471.0 
9,323.0 
9, 467. 0 
9, 455. 0 
9,471.0 
9,442.0 
9, 489. 0 
9, 489. 0 
9,619.0 
9,621.9 
9, 130. 0 
9,467.0 


3,714.0 
3, 722. 0 
3, 695. 0 
3,739.9 
3, 746. 0 
4, 340. 9 
4,379.3 
3,909.2 
3,714.5 
3,721.5 
3,659.0 
3, 762. 0 
3, 742. 6 
3,692.0 
3,754.0 
3,939.0 
3, 760. 0 
3,567.0 
3,755.0 
3, 732. 8 
3,961.7 
3,955.2 
3,866.0 
4,001.0 
3,921.0 
3,958.7 
4,176.0 


Refer- 
ences. 


Investiga- 
tors. 


1, 2     St.  &  L. 
10     M. 
1,2,10     St.  &L. 


2 

2,3 
2 

1,2 
2 
2 

2,3 
2 
1 
2 

2,3 
2 
2 
2 
2 
2 
2 
2 
2 
2, 3, 10 
2 
8 
1 

10 
10 
10 
10 

1 


2,10 

2 

3 

8 

1 

2 

10 

2,10 

2,10 

2,10 

10 


2, 6, 10 

8,2,6,10 

5, 2, 10, 4 

2,6,10 

2, 8, 6, 10 

2,6,10 

2, 6, 10 

2,6,10 

2,6,10 

2,6,10 

2,4 

2,4 

2,8,6,10 

2,4,5,10,1 

2,10 

1 

6 

1 

2,8,6,10 

2,10 

2,4,10,9 

8, 2, 6, 9, 10 

2, 5, 10 

2,10 

2,10 

9 

1 


St.  &  L. 

St. 

D. 

R. 

Gi. 

St.  &  L. 

St 

Gi. 

D. 

St.  &  L. 

St. 

Gi. 

St. 

St. 

St. 

St. 

St. 

Gi. 

St.  &  L. 

St. 

Gi. 

St. 

St.  &  L. 

St. 

R. 

St.  &  L. 

St. 


B.  &  M. 

St.  &  h. 

St. 

B.  &M. 

St.  &  L. 

St.  &  L. 

St.  &  L. 

St.  &  L. 

St.  &  L. 

St.  &  L. 

St. 

B.  &V. 

St.  &  L. 

St. 

Gi. 

Rch. 

B. 

Rch. 

St.  &  L. 

B.  &F. 

B.  &  V. 

St.  &  L. 

St. 

Ru. 

Gi. 

T. 

D. 


14 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


Table  I. — Heats  of  combustion  of  1-gram  substance,  expressed  in  small  calories — Cont'd. 


Substance. 


Formula. 


Calories. 


Refer- 
ences. 


Investiga- 
tors. 


carbohydrates,  etc. — continued. 

Cane  sugar  (sucrose) 

Do 

Do 

Milk  sugar  (lactose) 

Do 

Do 

Do 

Milk  sugar  hydrated 

Do 

Do 

Do 

Do 

Do 

Do 

Do 

Do 

Maltose 

Do 

Maltose  hydrated , 

Do 

Trehalose 

Trehalose  hydrated 

Rafflnose  (melitriose) 

Do 

Do 

Rafflnose  (melitriose)  hvdrated 

Do 

Melitose 

Do 

Melezitose 

Glycogen 

Cellulose 

Do : 

Do 

Do 

Do 

Do 

Dextrin  (dextran ) , 

Do 

Starch 

Do 

Do 

Do 

Do 

Do 

Iniilin 

Do 

Do 

Do 

ALCOHOLS. 

Methyl  alcohol  (liquid)  

Do 

Do 

Methyl  alcohol  (gas) 

Kthvl  alcohol  ( liquid) 

Do 

Do 

Do 

Do 

Kthvl  alcohol  (gas) , 

Do 

Do 

Propyl  alcohol  (liquid) 

Do 

Propyl  alcohol  (gas) 

Do 

Amy]  alcohol 

Do  !"!!!!!"*"!"w"!!Il!"*" 

Glycerin 

Do 

Do 

DO 

Do 

Krvthrit 

Do 

Do 

!"•    

Do 


C^H^O, 
C,.,Ho.,Oi 
C^H^C-! 
C^HjaO, 
CiorUO, 
C^Ho.,0, 

c,;h.»o, 

CVHooO, 
C,oH*,0, 

c^h:»o, 

CisHj.0] 

C^H^C-! 
Cj.H«0, 
CfcHaO] 
C^Ho.0, 

c,:h„Oi 

C^H^O, 
CwHhO, 

c,;h^o, 

C^HfflO, 

C12H.15O 

CigHajO 

CigH^O 

CigHgoO- 

C^HaoO 

CisHgoO 

C12HaO 

CioHajO 

C1SH34O. 

(CeHmO, 

(CH,oO. 

(C0H„A 

(C6Hj0O6)n 

(C(H10O5n 

(CcH,n05)n 

(CoH„(06)n 

(CflH„,05)n 

(C8H1005)n 

(C«H1()05  11 

(C0H1()O5)n 

(C0Hu,()f,)n 

(CHwObJh 

(C6Hlft06)n 

(CaH,„06)n 

(CoH„,Or>)n 

MV.l  I,  ,,<  >;,)n 

(<Y.H„,<>.-,in 

ChH(oOii  . . 


H.,0. 

h:;o. 
h:,o. 
h«o. 

H20. 
HoO. 

h.;o 
h:.o 

H.0  . 


H..O. 

h,o. 


HoO 


(HoO) 
(HjO) 


CH40... 
CH40 . . . 
CH40... 

CR.O... 

•  '.1 1,1 1 .. 

c,II,,().. 
•'...I !..().. 
« •,!!..( ».. 
C-..H„0  . . 

<  ,1!..<)  .. 

«'•■  I !,■,(»  .. 
(\II.u  .. 
c.M.o 
c.ll.o  .. 
(Ml.o  .. 
r,ll,,o.. 
C5H,sO.. 
c. I !,,().. 

<:M    " 

•Ml.".  . 
«"..1U»., 
«-,H-«»,  . 

«;,;;.«», 
I    II   o< 

1  ,ii  0 

::!!  8; 

1  ,n  '  \ 


4, 173. 0 
3,959.0 
908.0 
951. 5 
877.0 
162. 0 
920.0 
777.1 
736.8 
663. 0 
710.0 
945.0 
667.0 
772.2 
721.8 
724.0 
949.3 
163.0 
721.8 
932.0 
917.0 

550. 3 
928.0 
020.0 
020.8 
400.2 
399.1 
880.0 

122.  2 
913.7 
190.6 
200.0 

185. 4 
146.0 
152. 9 
155.0 
205.  0 
180.4 
112.3 
228.  0 
182.5 

123.  0 
164.0 
479.0 
116.0 
187.1 
133.5 
070.0 
133.5 


5, 260. 7 
5, 307. 1 
5,321.5 
5,693.7 
7,068.0 
7,188.6 
6,980.0 
7,095.0 
7,044.0 
7,402.2 
7,821.7 
7,394.1 
8,010.3 
8,005.2 
8,310.0 
7,301.7 
\  968.  'i 
9,021.8 
9,005.7 
(4,112.  I) 
1,812.  1 
4,317.0 
4,305.0 
4,265.2 
1,075.0 
1. 112.6 
4,117.6 
4,181.8 
4,132.3 


1 

1 

4 

2,6,10 

1,2,4,5,10 

1 

10 

2,10 

2, 8, 6, 10 

2, 4, 10 

2 

1 

1 

4 

6 

10 

2,8,6,10 

1 

2, 6, 10 

1 

2,10,6 

2, 10, 6 

10 

2,6,10 

2,6,10 

2,6 

10 

4 

5 

2,6,10 

2,6 

2,4 

2,6,10 

1,2,4,10 

6 

10 

10 

2,10 

2,10,6 

2,4,10 

2,6,10 

2,4,10 

2, 6, 10 

1 

1 

2,10 

2 

2,4,10 

6,10 


6 

10 

10 

10,5 

2,10 

3, 10, 1 

1 

9 

5 

10 

10 

5,7 

6 

10 

10 

5,7 

Hi 

10 

5 

2 

10 

2,10 

1 

10 

to 

10 

10 

10 

10,6 


Rch. 

St. 

St. 

St.  &  L. 

St. 

Rch. 

Gi. 

B.  &  V. 

St.  &  L. 

St. 

Gi. 

Rch. 

St. 

B. 

Gi. 

Gi. 

St.&L. 

Rch. 

St.  &  L. 

Rch. 

St.  &  L. 

St.  &  L. 

St. 

B.&M. 

St.  A:  L. 

St. 

St.&L. 

St. 

St. 

St.  &  L. 

St.  &  L. 

B.  &  V. 

St.  &  L. 

St. 

Go. 

Go. 

B.  &  V. 

B.&  V. 

St.  A:  L, 

B.&  V. 

St.  A.  L 

St. 

Gi. 

Rch. 

St. 

B.  &  V. 
St.&  L. 
St. 

St. 


F.  &8. 
St.  &  L. 
Th. 
it.  A  If. 

F.  &  S. 

B. 

A. 

St. 

Th. 

B.  &  M. 

St. 
Lu. 
Th. 

F.  &8. 

1,11. 
St. 

st.  A  I. 

St.  A:  L. 

St. 

St. 

Lu. 

St. 

Lu. 

B.  A  M. 

si.al.ak. 

St.  &  L. 


EARLIER    DETERMINATIONS. 


15 


Table  J. — Ileal*  of  combustion  of  1-gram  substance,  depressed  vn  small  calorics — Cont'd. 


Substance. 


alcohols — continued. 


Erythrit C4H,0O4 . 

Mannite CcH140„. 

Do CcHH0„. 

Do C„HM0„. 

Do Cr)HM0(1. 

Do C6HI40„. 

Do C„H14O0. 

Arabit C5H,»O0. 

Dulcit c(-,n,4o,-,. 

Do CUu'V,. 

Do I  CsHhOo- 

Quercite ' C<iHluO0. 

Do I  CfiH1205. 

Inostte I  CoHvOo . 

Do CoHioOc- 


Formula. 


a  cms. 


Formic  acid  (liquid) CH.,Oo  . 

Do ch;o„  . 

Do CH202. 

Formic  acid  (gas) CH202  . 

Acetic  acid G>H40.> 

Do    QtgA 

C2H4C).j 
C2H40., 
C2H40.j 
C2H402 
C2H402 


Do 

Do 

Do 

Do 

Acetic  acid  (gas). 

Propionic  acid C3HG02 

Butyric  acid C4H802  . . 

C4Hjt02  . . 
C4H802  .  - 
C4Hfi03. .. 

Cl6H3o02  . 

Ci0H32O2  . 
CieH^Oo  . 
C16H30O2 . 

C10H32O2  . 

CisHajO.) . 
Ci8Ha602  . 

C^HggOo  . 

CisHjeOo  . 
C,8H:)402  . 
C3H404.. 
C3H404.. 
C.!H]04... 
C4H604.. 
C4H604.. 
C4Hc04  . . 
C4H604.. 
C4H0O4.. 
C4H(jOo 


Do 

Do 

Oxybutyric  acid 
Palmetic  acid. . . 

Do 

Do 

Do 

Do 

Stearic  acid 

Do 

Do 

Do 

Do 

Oleic  acid 

Malonic  acid 

Do 

Do 

Succinic  acid  . . . 

Do 

Do 

Do 

Do 

Tartaric  acid 

Do C4H606  . 

Citric  acid C6HgOT 

Do C0H8O7 

Do C0H8O7 

Citric  acid,  hydrated C«H807H-,0 

Oxalic  acid C5H0O1 


Do 

Do 

Do 

Do 

Benzoic  acid.. 

Do 

Do 

Do 

Do 

Do 

Do 

Salicylic  acid 

Do 

Do 


HYDROCARBONS,   ETC. 


Methane  . 

Do  ... 

"    Do... 

Do... 


CjH.204 

C2H„04. 
C2H..,04. 
(>oH.)04. 
C7H0O2. 
C7H,j02. 
C7H0O2. 
07Ho02. 

<';1I„0... 
C-ll,(l... 

C-H.A- 

C-H.,<>:. 
C-H,'  •  ,;■ 
C7H..M,. 


CH4. 
CH4. 
CH4. 
CH4. 


Calorics. 

Refer- 
ences. 

Investiga- 
tors. 

4,072.7 

5 

St. 

4,001.2 

2,4,10 

B.&V. 

3, 997. 8 

2, 6, 10 

St.  &  L. 

3,908.0 

2 

St. 

3, 959. 0 

2, 6, 10 

Gi. 

3, 939. 0 

10 

St. 

3, 930. 0 

5,10 

St. 

4, 024. 0 

6,10 

St.  &  L. 

3,975.9 

6,10 

St.  &  L. 

4,006.0 

4,10 

B.&V. 

3, 905. 9 

6 

St. 

4, 293. 6 

6 

St. 

4,329.0 

6 

B. 

3, 679. 6 

6 

St. 

3,695.1 

6 

B. 

1,271.2 

5 

St. 

1, 366. 8 

10 

J. 

1,347.8 

10 

B. 

1,508.5 

10 

Th. 

3, 490. 4 

2 

B.  &M. 

3, 505. 2 

1,10 

F.  AS. 

3, 498. 3 

7 

3, 553. 2 

5 

St. 

3, 480. 0 

10 

J. 

3,555.0 

10 

St.  &  R. 

3, 755. 0 

10 

Th. 

4,968.2 

5 

St. 

5, 936. 9 

5 

St. 

5,647.0 

1,10 

F.  &  S. 

5, 939. 8 

10 

St.  &  Ro. 

4,536.0 

10 

Lu. 

9, 352. 9 

2,10 

St.  &  L. 

9,226.0 

2,10 

St. 

9,216.8 

5 

St. 

9, 264. 8 

10 

Lu. 

9,316.5 

10 

F.  &S. 

9,429.0 

2,10 

St. 

9,716.6 

1,10 

F.  &S 

9,412.0 

1 

St. 

9,886.0 

1 

Rch. 

9, 745. 0 

1 

R. 

9, 494. 9 

10 

St.  &  L. 

1,998.2 

2,10 

B.  &  Lu. 

1,960.0 

2 

St. 

1,998.3 

10 

St.  &  L. 

3, 006. 2 

2,10 

B.  &  Lu. 

3,019.0 

2 

St. 

2,996.0 

1 

Rch. 

2,937.0 

1 

St. 

3, 026. 3 

10 

St.  &  L. 

1, 745. 0 

1.2 

St. 

1,407.0 

1 

Rch. 

2, 477. 9 

2,10 

B.  <k  Lu. 

2, 397. 0 

2,10 

St. 

2, 477. 9 

2,10 

B.  &  Lu. 

2,250.4 

10 

Lu. 

659.0 

1 

Rch. 

569.0 

1 

St. 

571.0 

10 

St. 

678.6 

10 

St.  &  L. 

672.5 

10 

J. 

6,360.5 

5 

St. 

6, 322. 3 

9 

St.  &  L. 

6, 322. 1 

9 

B.  &  Lu. 

6,281.0 

10 

St. 

6,315.0 

10 

St.  &  Ro. 

6, 345. 0 

10 

B.  &  Re. 

(7, 663. 0) 

5 

St. 

7,236.0 

5 

St. 

5,286.2 

10 

St.  &  L. 

5, 326. 0 

10 

B.  &  Re. 

13,063.0 

3,10 

F.  &S. 

13,218.9 

5,7 

Th. 

13, 243. 7 

10 

Th. 

13, 275. 0 

10 

B. 

16 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


Table  I. — Heat*  of  combustion  of  1-gram  substance,  expressed  in  small  calory's — Cont'd. 


Substance. 


Formula. 


Calories. 


Refer- 
ences. 


Investiga- 
tors. 


hydrocarbons,  tttc. — continued 

Ethane 

Do 

Do 

Propane  

Do 

Do 

Acetylene 

Do 

Do 

Ethylene 

Do 

Do 

Do 

Propylene 

Do 

Do 

Benzol  (benzene) 

Do 

Do 

Benzol  (gas) 

Do 

Do 

Naphthalene 

Do 

Do 

Do 

Do 

Do 

Camphor  (inactive  solid ) 

Do 

Do 


C»Ho 

C,H0.r... 

CJH^ 

CjHg 

CgH8 

CgHg 

CjHo 

C2HJ 

CjHo 

C2H4 

C2H4. . . . . 
C2H4 

C3H0 

CiH0 

CgH| 

C„HC 

CflH0 . 

C()H,; 

Cr,Ho 

<V,Ho, 

CoHf, 

Ci<)H8 

^ioH« 

CjioHs 

Ci0H8 

CuiHj 

CioHg 

C,oH()„;0 
CloHOK,0 
C,0HO,c() 


12,144.2 
12, 346. 7 
12,991.7 
12,027.3 
12, 543. 0 
12, 582. 0 
11,919.7 
11,923.0 
12, 112. 0 
11,858.0 
11,894.4 
11,883.6 
12, 154. 0 
11, 730. 0 
12, 045. 0 
11,717.0 
9, 949. 0 
9,977.5 
9, 997. 0 

10,041.0 
10,096.0 

10,247.4 
9, 628. 0 
9. 618. 7 
9, 664. 0 
9, 700. 0 
9,718.0 
9, 773. 0 
9, 298. 7 
9,291.6 
9,288.0 


7,5 
10 
10 
10 

10 

5,7 

7 

10 

10 
3,10 

7,5! 
10 
10 
10 
10 

5,7 
10 
10 
10 

10 
10 

10 
9,10 
10 
10 
10 
10 
10 
10 
9 
9 


Th. 
B. 
Th. 
B. 

Th. 
Th. 
B. 
F.&S. 

Th. 
B. 
Th. 
B. 

B. 

St.  &  L. 

St.,   Ro.  & 

He. 
B.  &  Og. 
St.,  Ro.  & 

He. 
Th. 

St.  &  L. 
St.  &  L. 
B.  <&R. 
B.  &  Lu. 
B.  A:  V. 
Ru. 
Lu. 
St. 
B. 


Nearly  all  of  these  results  were  obtained'  by  burning  the  substance 
in  oxygen  gas  in  the  bomb;  but  if  we  examine  and  compare  the  heat 
values  obtained  by  different  investigators  with  the  same  compound, 
and  note  how  one  author  quotes  the  results  of  one,  and  another  those 
of  a  second,  investigator  as  being  the  correct  ones,  we  reach  but  one 
conclusion,  namely,  that  some  one  is  wrong.  Two  different  results 
can  not  both  be  correct.  The  differences  are  in  many  instances  so 
great  that  they  can  not  possibty  be  ascribed  to  impure  substances  or 
ordinary  analytical  errors  due  to  drying,  weighing,  etc.  But  who  will 
take  the  responsibility  of  saying  that  one  investigator  is  right  and 
another  wrong?  Or  that  so  much  of  one  man's  work  and  so  much  of 
the  work  of  some  one  else  is  correct?  Each  of  the  two  men  whose 
names  appear  most  frequently  (Stohmann  and  Berthelot)  has  a  large 
following.  Many  will  accept  Stohmann's  results  before  those  of  any- 
one else,  and  the  same  may  be  said  of  Berthelot;  yet  there  is  nothing 
which  indicates  that  there  was  some  particular  fault  in  the  operation 
of  one  distinct  from  the  other,  for  in  some  cases  Stohmann,  and  in 
others  Berthelot,  has  the  higher  figures  for  the  same  substance. 

Judging  from  the  records  of  the  different  investigators,  the  most 
that  can  be  said  is  that  with  a  few  substances  we  have  the  heats  of 
combustion  to  within  the  limits  of  analytical  error,  but  with  the 
majority  only  approximately  so,  and  with  a  few  not  even  that. 


VARIATIONS    IN    DETERMINATIONS. 


17 


Evident!}7  there  is  need  of  a  revision  in  the  heat  values  of  organic 
substances  so  that  only  the  reliable,  or  at  least  nearly  correct,  values 
should  lind  their  wa}7  into  the  tables  of  text-books,  etc.,  and  the  faulty 
ones  be  dropped.  Until  such  a  systematic  checking  up  of  the  older 
results  by  means  of  the  very  best  and  most  modern  apparatus  has  been 
done,  the  bomb  calorimeter  should  be  used  freely  in  all  investigations 
where  the  heats  of  combustion  play  a  part,  and  the  values  found  by 
actual  determinations  should  be  preferred  to  those  obtained  or  com- 
puted from  general  tables.  The  bomb  thermometer  may  also  to  a 
limited  extent  serve  as  a  standard  with  which  other  thermometers  in 
use  may  be  compared. 

VARIATIONS   IN    DETERMINATIONS   ALREADY   ON   RECORD. 

In  order  to  make  these  figures  a  little  plainer  and  to  put  the  matter 
in  more  compact  form  I  have  selected  some  of  the  more  common  com- 
pounds from  the  previous  table,  and,  placing  the  highest  reported  heat 
of  combustion  of  a  substance  at  100,  have  shown  in  the  following  table 
the  difference  between  it  and  the  lowest  result  obtained  b}r  some  other 
investigator: 

Table  II.  —  Difference  between  the  highest  and  lowest  results  on  some  common  compounds 

referred  to  in  Table  J. 


Substance. 


Hydrogen 

Charcoal 

Sulphur 

CO  to  C02 

Hemoglobin... 
Milk  casein... 
Egg  albumin  . 
Blood  fibrin  .. 

Peptone 

Chondrin 

Urea , 

(ilycocoll 

Hippuric  acid . 

Asjiarngin 

Uric  acid 

Fat  of  swine... 

Fat  of  oxen 

Butterfat 

Olive  oil 

Arabinose 

Galactose 

Dextrose 


|  Number 
:  of  inves- 

Differ- 

tigators. 

il 
Per  cent. 

8 

1.86 

i 

4.58   ; 

4 

4.33  1 

0 

1.60    1 

S 

1.09    1 

8 

4.10 

4 

2.72    ! 

i 

4. 52 

4 

7.98 

3 

8.11 

6 

16.53 

4 

2.  <17 

3 

.46    ! 

3 

3.34 

4 

4.83 

5 

3.16 

4 

3.40 

6 

.57 

7 

i.56 

3 

.73 

2 

1.68 

6 

1.86 

Substance. 


Number 
of  inves- 
tigators. 


Cane  sugar 

Milk  sugar 

Milk  sugar,  hydrated 

Maltose 

Maltose,  hydrated 

Cullulose , 

Starch , 

Inulin , 

Methyl  alcohol  liquid 
Ethyl  alcohol  liquid. 

Glycerin 

Mannite 

Acetic  acid , 

Palmetic  acid 

Stearic  acid 

Oxalic  acid 

Benzoic  acid 

Methane 

Benzol  liquid  ..x 

Benzol  gas.  

Naphthalene  

Camphor 


Differ- 
ence. 


Per  cent. 
6.42 
6.85 
7.17 
5.13 
5.35 
1.40 
2.65 
2.75 
1.18 
2.83 
1.20 
2.33 
2.11 
1.46 
4.80 
16.08 
1.25 
1.60 

.48 
2.02 
1.58 

.12 


In  chemical-laboratory  work,  whether  it  be  by  advanced  students 
or  professional  chemists,  it  is  required  that  the  work  of  the  analyst 
shall  be  within  certain  limits  of  error,  varying,  naturally,  with  the 
nature  of  the  substance  analyzed  and  the  method  employed.  No  fixed 
rule  can  be  laid  down  as  to  the  limits  of  error  allowed,  but  for  most 
of  the  more  common  substances — such  as  oxides,  carbonates,  many 
ores  and  clays,  etc. — some  of  which  have  many  ingredients  to  be 
18399— No.  94—07 3 


18  INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 

determined,  the  total  of  the  determinations  must  come,  barring  excep- 
tional cases,  within,  say,  about  99.75  per  cent  and  100.5  per  cent,  in 
order  to  be  accepted.  The  extent  to  which  the  results  obtained  by 
different  analysts  on  a  single  ingredient  are  allowed  to  vary  is  very 
variable.  In  a  determination  like  that  of  total  nitrogen,  for  example, 
the  substance  containing  18  per  cent  nitrogen,  two  analysts  should 
come  not  farther  than  about  0.05  or  0.06  per  cent  apart  in  the  results 
obtained,  except  for  special  reasons.  Such  a  variation  as,  for  instance, 
between  17.97  per  cent  and  18.03  per  cent  nitrogen  would  be  equal  to 
0.33  per  cent  difference  between  the  analysts. 

Of  the  44  cases  just  cited  in  Table  II  the  difference  between  the 
Jesuits  obtained  b}r  different  investigators  is  below  1  per  cent  for  only 
five  substances.  With  most  of  the  substances  the  anatysts  are  several 
points  apart,  and  in  urea  and  oxalic  acid  there  are  difference's  of  over 
1»>  per  cent. 

That  two  determinations  by  the  same  analyst  agree  when  the  same 
quantity  of  the  sample  is  used,  under  exactly  the  same  conditions  and 
manipulations,  is  no  guaranty  that  the  method  is  perfect  or  the  result 
correct.  If,  on  the  other  hand,  results  agree  when  charges  varying  in 
weight  have  been  used  under  somewhat  varying  conditions  within  the 
working  limits  of  the  method,  we  feel  more  sure  about  their  being 
correct. 

CAUSES  OF  DIFFERENCES  IN  HEAT  DETERMINATIONS. 

The  method  for  the  determination  of  heat  values  of  substances  can 
not  be  considered  perfect  until  work  can  be  done  as  accurately  as  is 
possible  in  ordinary  chemical  anal}Tses  at  least. 

From  the  heat  values  given  we  are  led  to  question:  What  can  have 
caused  these  differences  in  the  pa^t?  What  causes  differences  at 
present  i 

Following  the  directions  given  in  Wiley's  Principles  and  Practice 
of  Agricultural  Analysis,  Volume  III,  a  number  of  determinations 
had  been  made  In  this  laboratory  by  means  of  the  apparatus  already 
described,  using  the  commercial  oxygen  gas  found  on  the  market,  put 
up  in  iron  cylinders  under  very  high  pressure.  The  water  equivalent 
of  the  whole  bomb  system  had  been  determined  by  burning  cellulose 
:m<l  cane  sugar  in  oxygen  under  20 atmospheres'  pressure  in  the  bomb. 
4,185  calories  per  gram  being  the  heat  value  used  for  the  cellulose 
and  :;.:».V>. 2  calories  per  gram  tor  the  sugar.  The  average  of  a  large 
number  of  determinations  had  given  the  value  as  480  grams,  and 
since  exactly  2,000  grama  of  water  was  used  in  all  cases,  the  factor 
irae  2,480. 

Apparently  there  was  no  difficulty  in  obtaining  concordant  results 
when  like  charges  wciv  burned,  but  with  varying  charges  the  work 
was  not  satisfactory.    The  analytical  error  with  a  small  eharge  may  of 


CAUSES    OF    DIFFERENCES    IN    HEAT    DETERMINATIONS.  19 

course  magnify  the  percentage  error,  but,  excluding  this  possibility,  it 
should  be  possible  with  a  small  charge  to  obtain  results  indentical  with 
those  obtained  from  a  larger  charge  of  the  same  material.  To  say  that 
4,000  to  5,000  calories  should  be  generated  in  the  bomb  in  order  to  give 
good  results,  and  that  with  only  2,000  calories  the  work  is  not  satis- 
factory, is  to  say  that  the  entire  method  is  unreliable. 

IMPURE   OXYGEN. 

Some  difficulties  which  were  experienced  in  elementary  carbon  and 
hydrogen  determinations  in  which  the  same  oxygen  was  used  led  to 
the  examination  of  the  oxygen  for  impurities  in  the  form  of  combus- 
tible gases.  It  was  found  beyond  a  doubt  that  such  impurities  were 
present  in  the  oxygen  in  quantity  sufficient  to  be  reckoned  with,  and 
the  magnitude  of  the  error  caused  by  them  will  be  referred  to  further  on. 

Now  arose  the  questions:  To  what  extent  do  these  combustible  gases 
influence  the  working  of  the  bomb  calorimeter?  Is  the  water  value  of 
the  bomb,  determined  by  the  use  of  this  impure  oxygen,  correct?  Can 
a  correction  and  the  water  value  be  worked  out  correctly? 

TESTING    OF   OXYGEN. 

In  order  to  give  the  apparatus  a  severe  test  and  to  try  to  work  out 
an  answer  to  some  of  these  questions,  using  the  impure  oxygen  itself 
for  the  purpose,  the  following  method  was  adopted:  Cellulose  was 
chosen  as  the  chief  substance  to  be  burned,  and  sugar  in  the--  form  of 
rock  cand}'  was  also  used.  B}r  burning  small  charges  of  pure  cellulose 
absorption  blocks  in  the  bomb  calorimeter,  charged  with  oxygen  at 
various  pressures,  it  was  hoped  that  any  increase  found  with  the 
greater  pressure  of  oxygen  would  represent  the  total  imparity  in  the 
additional  amount  of  oxygen  equivalent  to  the  increased  pressure,  and 
that,  having  ascertained  the  correction  for  impurities,  it  could  be 
applied  and  the  water  value  of  the  bomb  worked  out  without  difficult}'. 
Cellulose,  although  a  very  hygroscopic  substance,  and  on  that  account 
difficult  to  handle,  was  chosen  for  this  work  because  it  ignites  readily 
and  burns  quickly  and  completely  in  a  comparatively  small  excess  of 
oxygen.  It  represents  the  main  class  of  substances  whose  heats  of 
combustion  are  determined  in  our  work,  and  its  heat  value  is  fairly 
well  established.  Sugar,  on  the  other  hand,  is  a  substance  which  does 
not  ignite  readily  and  which  burns  more  slowly,  often  leaving  a  trace 
of  unburned  carbon  even  with  plenty  of  oxygen. 

It  was  soon  learned  that  the  combustible  gases  in  the  oxygen  were 
not  oxidized  completely,  and  perhaps  never  can  be  fully  burned  in  a 
bomb  calorimeter,  but  the  tests  were  carried  out  as  planned.  The 
problem  was  not  so  simple  as  at  first  thought,  but  it  was  hoped  that 
the  oxidation  of  the  gases  referred  to  would  be  in  proportion  to  the 
densitj-  of  the  gas  mixture  or  the  heat  generated  in  the  bomb.     This 


20  INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 

is  by  no  means  a  perfect  method,  but  it  may  be  a  means  of  helping 
over  the  difficulty  when  no  pure  oxygen  or  other  means  for  compari- 
son are  at  hand.  * 

One  lot  of  oxygen  (Oxygen  I)  was  tested  with  both  cellulose  and 
sugar  in  the  manner  described.  A  second  lot  (Oxygen  II)  was  tested 
only  with  cellulose.  In  every  instance  the  cellulose  was  dried  at 
between  103°  and  105°  C.  to  constant  weight. 

The  effect  of  the  impurities  may  be  seen  in  Tables  III  to  VII, 
where  the  corrected  rises  in  temperature  will  indicate  the  differences 
due  to  more  or  less  oxj^gen  and  to  the  amount  of  heat  generated  in  the 
bomb.  But  before  we  discuss  these  results  we  may  examine  Table  III, 
where  we  find  the  heats  of  combustion  of  the  various  substances  worked 
out  as  in  the  course  of  ordinary  routine  work,  using  the  water  value 
430  for  the  bomb  system.  This  value  plus  the  2,000  grams  of  water 
used  makes  the  factor  for  the  bomb  system  plus  water  equal  to  2,430 
grams. 

The  column  headed  ''Total  computed  calories "  refers  to  all  the 
heat  generated  in  the  bomb,  and  includes  the  heat  represented  by  the 
substance  and  the  iron  wire  burned,  the  nitric  acid  formed  and  dis- 
solved, and  the  heat  due  to  the  electric  current  whenever  it  failed  to 
ignite  the  substance  instantly. 

Varying  amounts  of  oxygen  will  change  the  water  value  of  the  sys- 
tem:  hence  in  all  cases  where  more  or  less  than  20  atmospheres  oxygen 
wa>  used  the  temperature  rises  have  been  corrected  to  20  atmospheres 
oxygen  pressure.  For  this  bomb-— of  about  360  c.  c.  capacit}' — the 
correction  fori  atmosphere  oxygen  is  ±0.0046  percent  of  the  observed 
rise  in  temperature.  Thus,  taking  for  example  the  first  rise  referred 
to  in  Table  III,  the  rise  due  to  the  burning  of  0.5092  gram  sugar  in  10 
atmospheres  oxygen,  corrected  to  20  atmospheres  oxygen,  will  be: 

°c. 

Observed  rise  in  temperature. 0.  8488 

Correction  for  10  atmospheres  oxygen 00039 

Correct e<l  rise 84841 

The  heat  values  accepted  for  the  following  substances,  and  used  in 
the  computations  of  the  bomb  water  values  given  in  Table  III.  are: 

Calories  per  gram. 

Cellulose 4, 185.  1 1 

Sugar 3, 955.  2 

Naphthalene 9,028.0 

Camphor 9,290.0 

lien/.,  tie  acid 6,  322.  0 

The  water  values  of  the  bomb  as  found  worked  out  in  Table  III 
have  not  been  used  in  any  computation,  hut  they  will  indicate  how 
widely  the  individual  values  vary  from  43U  the  value  used  in  the  cal- 
culations of  heats  of  combustion. 


TESTING    OF    OXYGEN.  /   ^'V/l/c-,  '  %l 

Table  III. —  Water  value  of  the  bomb  calorimeter  and  heat  value  p&gram  of  subetan 
worked  out  by  asina  tin-  hotter  value  iSO.a  PRmh^Jr 


Substance. 


Sugar 

Cellulose 

Cellulose 

Naphthalene 

Camphor 

Benzoic  acid 


Lot  of 

oxygen 

used. 


1. 
I. 

II 

II 

11 
II 


Oxygen 

Weight  of 

Total  com- 

pressure. 

substance. 

puted. 

Atmospheres, 

Grams. 

Valor  ir.<. 

10 

0.5092 

2, 050. 26 

10 

.5019 

2,013.96 

24 

.5054 

2,038.32 

24 

.509(5 

2,046.85 

24 

1.0000 

4,106.14 

10 

.3799 

1,617.47 

10 

.3840 

1 ,  (128. 16 

10 

.3711 

1,571.58 

15 

.3789 

1,604.70 

20 

.3800 

1. 609.  68 

20 

.  3737 

1,581.11 

20 

.3714 

1,574.21 

20 

.6800 

2,868.06  ! 

10 

.4358 

1,802.34 

10 

.  4257 

1, 803.  55 

24 

.  4253 

1,824.37 

24 

.  4276 

1,815.50 

24 

.6675 

2,817.39 

24 

1.0035 

4,229.14 

20 

.  5274 

5,108.42 

20 

.5430 

5,255.04 

20 

.4671 

4,360.28 

20 

.5034 

4,703.37 

20 

.6986 

4,438.67 

20 

.7027 

4, 473. 37 

Rise  cor- 

rected for 

Bomb 

oxygen,  20 

water 

atmos- 

value. 

pheres. 

°C. 

0.8484 

416.6 

.8352 

411.3 

.8493 

400.1 

.  8558 

390.1 

1.7037 

410.0 

.6671 

424.6 

Calories 

per 
gram. 


.  6746 
.6484  i 
.6678 
.6734  ! 
.6604  j 
.6558 
1.1896  ! 
.  7381 
.7395 
.7489  ! 
.7450  : 
1.1579  i 
1.7492 
2.1111  | 
2. 1785 
1. 7985 
1.9409 
1. 8390 
1.8520 


413. 5 
423.8 
403.1 
390.4 
398. 7 
400.4 
410.9 
442.0 
438.7 
435.9 
436.8 
433.1 
417.7 
419.8 
412.2 
424.4 
423.3 
413.6 
415.4 


3,976.0 
3,983.1 
4,005.4 

4. 020. 2 
3,986.6 
4,194.4 

4. 213. 8 
4,193.3 

4. 232. 3 
4,255.2 
4, 240. 2 
4,237.2 
4,218.3 
4,164.2 
4,169.8 
4,174.5 
4,173.4 
4,179.5 
4,206.4 

9. 668. 9 
9,699.3 
9,311.6 
9,315.8 
(1, 365. 1 

6. 360. 4 


"No  correction  for  impurities  in  oxygen  is  applied. 

These  determinations,  too  few  in  number  for  very  good  averages, 
were  made  now  and  then  as  other  work  permitted;  hence  they  cover 
months  of  time.  A  hast}-  glance  over  these  tigures  would  be  enough 
to  condemn  the  apparatus  as  being  useless  for  accurate  work  or  the 
investigator  as  being  unskilled  or  careless.  Of  course  the  analytical 
errors  of  the  small  charges  will,  as  already  said,  be  magnified;  hence 
the  duplicates  may  not  always  agree  closely.  Looking  a  little  closer 
at  the  table,  we  notice  that  all  the  different  groups — that  is,  those 
which  were  treated  alike  as  toquantit}*  of  substance  and  the  amount  of 
oxygen — agree  fairly  well,  thus  proving  that  the  differences  between 
the  groups  are  not  due  to  careless  manipulation.  The  reason  for  the 
disagreements  must  be  sought  for  elsewhere. 

But  how  are  we  to  interpret  the  tigures,  which,  in  some  cases,  appar- 
ently contradict  each  other?  In  the  column  giving  calories  per  gram 
we  find  in  the  case  of  cellulose  an  extreme  difference  of  over  2  per  cent 
in  the  heat  of  combustion.  Further,  we  notice  that  0.5  gram  sugar 
burned  in  10  atmospheres  oxygen  gave  as  high  results  as  when  1  gram 
sugar  was  burned  in  24  atmospheres  oxj'gen.  Again,  in  the  case  of 
cellulose  in  Oxygen  I,  the  smaller  charges  at  20  atmospheres  oxygen 
gave  higher  results  than  the  larger  charge  at  the  same  oxygen  pressure, 
whereas  in  the  case  of  Oxygen  II  the  opposite  is  shown. 

Another  very  marked  peculiarity  in  the  results  is  that,  with  the 
same  factor  for  the  bomb,  etc.,  and  the  same  kind  of  cellulose,  in  the 
work  writh  Oxygen  I,  all  the  results  on  both  sugar  and  cellulose  are 
above  the  accepted  values — sugar  as  much  as   !.*>  per  cent  and  cellu- 


22 


INVESTIGATIONS    IN    I'SE    OF    BOMB    CALORIMETER. 


lose  up  to  1.64  per  cent.  In  Oxygen  II,  on  the  other  hand,  all  the  cel- 
lulose results,  except  the  one  where  over  1  gram  cellulose  charge  was 
used,  are  below  the  accepted  heat  value;  but  the  naphthalene,  camphor, 
and  benzoic  acid  are  all  above — naphthalene  about  0.7  per  cent,  cam- 
phor about  0.3  per  cent,  and  benzoic  acid  about  0.7  per  cent.  It  should 
be  mentioned  here,  however,  that  these  substances,  while  bought  as 
chemically  pure,  were  not  tested  for  impurities  before  using. 

Looking  at  the  column  giving  the  water  values  of  the  bomb,  we  find 
a  corresponding  variation,  most  of  the  values  being  below  the  one  used 
(430),  ranging  anywhere  from  390  to  442. 

If  a  general  view  is  taken  of  the  various  results  and  the  behavior  of 
the  substances  under  different  conditions,  we  are  convinced  that  the 
oxvgen  contains  considerable  impurity  in  the  form  of  combustible 
gases,  for  which  corrections  must  be  applied.  This  being  the  case,  the 
old,  apparently  too  high,  water  value  (430)  of  the  bomb  will  not  be 
high  enough. 

CORRECTION    FOR    IMPCRITY    IN    THE   OXYGEN. 

Is  the  correction  a  constant  quantity?  Is  it  of  any  value  to  know 
the  total  amount  of  carbon  and  l^drogen  present  as  combustible  gases 
in  the  oxygen?  These  are  some  of  the  questions  which  now  concern 
us  as  we  endeavor  to  work  out  the  water  value  of  the  bomb  system, 
applying  the  corrections  as  found  for  the  oxj'gen  and  for  the  amount 
of  heat  generated  in  the  bomb. 

We  turn  our  attention  to  Tables  IV  to  VII  and  examine  first  the 
work  with  cellulose,  Oxygen  I.  From  Table  IV  we  learn  that  between 
the  averages  computed  to  be  due  to  like  charges  burned  in  ten  atmos- 
pheres oxygen  pressure  and  20  atmospheres  there  is  a  slight  differ- 
ence in  the  rise  in  temperature  in  favor  of  the  greater  amount  of  oxy- 
gen. This  difference  does  not  represent  the  total  impurity  in  that 
amount  of  oxygen,  but  only  the  amount  which  will  be  oxidized  under 
the  specific  conditions  of  so  much  cellulose  and  so  much  oxygen.  The 
difference  in  rise  in  temperature,  when  about  1,600  calories  were  gen- 
crated  in  the  bomb,  was  0.000668    C.  for  1  atmosphere  oxygen. 

Tablb  IV. — Rite  in  temperature  <-<tnxi<l  by  burning  lite  quantities  of  cellulose  in  the 
homb  calorimeter,  in  varying  amounts  of  oxygen  I  Oxygen  I). 


i  ixyirin  preamre. 

Cellulose. 

Klis.- 

WIIV. 

11  No  . 

Total 

com- 
puted. 

Kise  in 

tempera- 

lure. 

Rise  cor- 
rected for  Rise  due 
oxygen,    to  1.600 
20atruo.t-  calories. 

pIllTi'S. 

Umotpht  n". 
10 

Oram. 
0.  8799 

.3711 
8789 

.8800 

.  :m~ 
.3714 

i  \doriet. 
17.12 
17. 12 
16.48 
16.00 
15.88 
15.66 

1  6.00 

Caloric*. 

■>.  60 
1.00 
2.00 
3.00 
:■,  Tii 
4.60 
3.90 

Calories. 
1,617.47 
1,628.16 

1,S7I.I)K 
1,604.70 
1,609.68 

1 .  5K4.  1 1 
1     .71  ?l 

°C. 
0. 6674 
.  ti749 
.6487 
.6679 
.6784 
8604 
.6558 

°c. 

0. 6671 
.  87  16 
.  IV4S4 
6678 
.6734 
.6604 
.  6658 

°c. 

0  6599 

10 

10 

15 

6868 

20 

20 

39. 

.  6670 
.6665 

CORRECTION    FOR    IMPURITY    IN    THE    OXYGEN. 


23 


°C.  I\x-. 

1 ,600  calories  in  20  atmospheres  oxygen  pressure . 0.  66763 

1,600  calories  in  10  atmospheres  oxygen  pressure 66098 

Difference 00665 

Rise  per  atmosphere  oxygen  pressure 00066") 

Whether  this  error  is  uniform  throughout — that  is,  whether  the 
eleventh  atmosphere  oxygen,  for  instance,  would  show  the  same  error 
as  the  t we n ty-tirst  atmosphere  with  the  same  charge — can  not  be  ascer- 
tained from  these  figures.  At  present  we  can  only  assume  the  error  to 
be  uniform. 

Is  this  then  the  true  correction  to  apply,  no  matter  how  large  a 
charge  was  burned,  or  will  more  of  the  gases  be  oxidized  in  the  same 
quantity  of  oxygen  when  more  heat  is  generated? 

Hock  candy,  Oxygen  I. — In  Table  V  we  find  a  difference  in  the  rise 
of  temperature  between  10  and  24  atmospheres  oxygen  pressure  equal 
to  0.00045°  C.  per  atmosphere  when  about  2,000  calories  are  generated 
in  the  bomb. 

Table  V. — Rise  in  temperature  caused  by  burning  like  quantities  of  rock  candy  in  the 
bomb  calorimeter  in  varying  amounts  of  oxygen  (Oxygen  /). 


Oxygen  pressure. 


Atmosphere* 

10 

10 

24 

24 


Rise  cor- 

Rock 
candy. 

Fuse 
wire. 

Total 

Rise  in 

rected  for 

HN03. 

com- 

temper- 

oxygen, 

puted. 

ature. 

20  atmos- 

pheres. 

Grams. 

Calories. 

Calories. 

Calories. 

°C. 

°C. 

0.5092 

18.08 

3.25 

2,050.26 

0.8488 

0.8484 

.5019 

16.80 

3.15     2,013.96 

.8356 

.8352 

.5054 

19. 52 

4.10  1  2.038.32 

.8491 

.8493 

.5096 

13.16 

4.50 

2,046.35 

.8556 

.8558 

Rise  due 
to  2,000 
calorics. 


°C. 

0.8276 
.8293 
.8333 
.8364 


°C.  rise. 

2,000  calories  in  24  atmospheres  oxygen  pressure 0. 83481 

2,000  calories  in  10  atmospheres  oxygen  pressure 82847 

Difference 00634 

Rise  per  atmosphere  oxygen  pressure 00045 

Sugar,  as  has  been  said,  does  not  always  burn  completely.  Fre- 
quently a  hardly  weighable  amount  of  carbon  may  be  seen  on  the 
platinum  capsule,  a  very  small  spot  perhaps,  yet  it  is  an  indication  of 
incomplete  combustion  of  the  carbon  itself  and  of  the  possibility  that 
at  least  traces  of  intermediate  partially  oxidized  products  may  be 
found. 

Cellulose,  Oxygenll. — In  Table  VI  we  find  the  results  obtained  with 
cellulose  and  another  lot  of  oxygen.  Here  1,800  calories  produced  in 
oxygen  at  10  and  24  atmospheres  pressure,  a  difference  in  temperature 
of  only  0.00007  C.  per  atmosphere,  which  is  within  the  limits  of 
analytical  error. 


24 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


Table  VI. — Rise  in  temperature  caused  by  burning  Wee  quantities  of  cellulose  in  llu 
bomb  calorimeter  in  varying  amounts  of  oxygen  (Oxygen  II). 


« >xygen  pressure; 

Cellulose. 

Fuse 
wire. 

HNOj. 

Total 
com- 
puted. 

Rise  in 
tempera- 
ture. 

Rise  cor- 
rected for 
oxygen, 
20  atmos- 
pheres. 

Rise  due 
to  1,800 
calories. 

10.. 

Atmospheres. 

Urams. 

0. 1258 

.4257 

.  4253 

.4276 

Calories. 
17.12 
19.20 
21.12 

21.44 

Calories. 
3.25 
2.80 
5.00 
4.55 

Calories. 
1,802.34 
1,803.55 
1,824.37 
1,815.50 

°C. 

0.7384 
.7404 

.7488 
.7449 

°C. 

0.7381 
.7395 
.7489 
.7450 

°C. 
0. 7371 

10 

.7386 

24.   .               

.7389 

•_>! 

.7387 

°  C.  rise. 

1,800  calories  in  24  atmospheres  oxygen  pressure 0.  73881 

1 ,800  calories  in  10  atmospheres  oxygen  pressure " . .     .  73778 

Difference 00103 

Rise  per  atmosphere  oxygen  pressure 00007 

We  have  reason  to  believe,  however,  judging  from  the  determina- 
tions referred  to  in  Table  III  that  this  oxygen  supply  also  was  not 
pure,  and  hence  we  take  up  the  question  asked  before:  What  effect 
has  increased  heat  production  upon  the  oxidation  of  these  combustible 
gases  J 

For  some  of  the  following  comparisons  1  must  depend  upon  single 
determinations,  which  in  itself  is  not  very  satisfactory;  but  since  no 
more  of  the  same  oxygen  is  at  hand  for  further  work  I  must  take  for 
granted  that  the  determinations  are  correct. 

Table  VII. — Comparison  of  observed  rise  in  temperature  due  to  the  large  and  the  calculated 
rise  due  to  the  smaller  charges  of  a  substance  burned  in  the  same  quantity  of  oxygen. 


Substance. 


Sugar I 


Lot  of 

oxygen 

used. 


•cllllloKe I 


(ellulottc. 


Oxygen  prcs-     Weight  of    Computed 
sure.         j  substance.        total. 


Atmotphera. 
24 

24 


arums. 
1.0000 
.  5075 


.6800 
.3750 


Calories. 
4,106.14 
2, 042.  33 


Rise. 


°C. 

1.70366 

1.713% 


1.0035 
.  1266 


.  8675 
1266 




2,068.81            .01020 

2,868.06  1         1.1890 
1,589.  SO          L1967 

1,278.76       -     .0071 

4,229.14  j        1.7492 
1,819.93  |         1.7359 

2,409.21        f  .0133 

2,817.39  |        1.1579 
1,819.98  '        1.1564 

997.46         f   .0015 


Observed. 

Calculated. 


Difference. 


Observed. 

Calculated. 


Difference. 


Observed. 

Calculated. 


Difference. 


Observed. 
Calculated. 


Difference. 


In  Table  VII  we  find  that  when  1  grain  of  sugar  was  burned  in  24 
Atmospheres  oxygen,  4,106.14  calorics  of  total  heat  being  generated 
in  the  bomb,  the  rise  in  temperature  of  the  bomb  system  was  found 
to  be  1.70366°  C.  The  avenge  rise  in  temperature  found  when  0.5075 
gram  of  sugar  was  burned,  or  2,042.33  calories  of  total  heat  was  gene- 


COMPARISON    OXYGEN    TESTS.  25 

rated  in  the  bomb,  in  the  presence  of  24  atmospheres  oxygen,  was 
0.8525°  C,  and  according  to  that  the  generation  of  4,106.14  calories 
should  have  caused  a  rise  of  1.71396°  (1  instead  of  1.70366°  C,  as 
found  when  1  gram  was  burned.  The  difference,  therefore,  is  a  minus 
of  0.0102°  C.  This  indicates  that,  of  the  impurities  in  this  particular 
oxygen,  more  were  oxidized  in  proportion  as  the  charge  of  sugar  was 
reduced.  Hence  the  correction  referred  to  in  Table  V  should  not 
be  increased  in  proportion  to  the  increase  in  the  amount  of  substance 
used. 

With  cellulose  in  Oxygen  I  a  charge  of  0.6800  gram,  which,  plus 
wire,  etc.,  was  equivalent  to  2,868.06  calories  total  heat  generated, 
gave  a  rise  of  1.1896°  C.  instead  of  1.1967°  C.  as  it  should  have  done 
according  -to  the  results  upon  the  smaller  charges.  Here  is  also  a 
minus  difference  of  0.0071°  C,  showing  that  this  oxygen  behaved  the 
same  with  these  two  different  substances.  The  combustible  gases 
present  in  the  oxygen  must  accordingly  be  of  an  easily  combustible 
nature,  comparatively  speaking,  when  the  increase  in  heat  has  no 
effect  upon  them  above  that  of  the  lesser  heat. 

Next  we  examine  the  results  obtained  with  different  amounts  of  cel- 
lulose in  Oxygen  II.  Here  we  see  not  a  decrease,  but  a  ver}^  marked 
increase  in  the  oxidation  of  combustible  gases  with  increase  in  heat 
evolved.  A  charge  of  0.6675  gram  cellulose,  or  a  total  heat  produc- 
tion of  2,817.39  calories,  gave  a  rise  in  temperature  of  1.1579°  C, 
which  is  0.0015°  C.  above  what  it  should  have  been  according  to  cal- 
culation from  the  results  of  the  smaller  charge  of  0.4265  gram  cellu- 
lose, equal  to  1,819.93  calories  total  heat.  When  1.0035  grams 
cellulose  was  burned  there  was  a  difference  of  0.0133°  C.  above  the 
calculated  result.  This  difference  in  behavior  of  the  two  oxygen  sup- 
plies toward  larger  charges  of  the  substances  burned  indicated  a  dif- 
ference in  composition  of  the  combustible  gases  in  the  oxygen.  In 
Oxygen  I  the  gases  were  apparently  more  readily  oxidized  than  in 
Oxygen  II,  and  therefore  more  of  them  burned  with  the  small  charges 
in  proportion  to  what  burned  with  the  larger.  The  opposite  would 
then  be  true  of  Oxygen  II.  Unfortunately  no  further  and  more  defi- 
nite proof  can  be  given,  since  no  qualitative  tests  were  made  of  the 
gases.  As  to  the  impurities  in  Oxygen  I  being  different  from  those 
in  Oxygen  II,  there  can  be  no  doubt.  In  the  first  lot  a  strong,  pecu- 
liar, disagreeable  odor  was  noticed,  and  when  the  gases  passed  through 
pumice  stones  saturated  with  H2S04  a  slight  3rellow  coloration  was 
noticed  for  a  short  distance.  Oxygen  II  had  no  such  disagreeable 
odor  and  did  not  color  the  pumice  stone  as  did  Oxygen  I. 

According  to  anatyses  made  by  one  of  the  assistant  chemists  of  the 
experiment  station,  Oxygen  I  contained  0.0355  per  cent  of  hydro- 
gen and  0.0150  per  cent  of  carbon  by  weight,  while  Oxygen  II  con- 
tained 0.0335  per  cent  of  hydrogen  and  0.0150  per  cent  of  carbon. 


26  INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 

These  results  show  that  there  must  have  been  considerable  free 
hydrogen  present. 

Not  knowing  the  composition  of  the  gases  referred  to,  we  may,  for 
the  sake  of  obtaining  at  least  an  approximate  calorific  value,  assume 
that  all  the  carbon  is  present  as  marsh  gas,  and  that  the  excess  of 
hydrogen  is  free  hydrogen.  Thus  we  have  in  Oxygen  I  0.02004  per 
cent  CH4  and  0.01446  per  cent  free  H2,  and  in  Oxygen  II  0.02004  per 
cent  CH4,  and  0.01346  per  cent  free  H2. 

With  20  atmospheres  oxygen,  or  in  round  numbers  10  grams  of 
oxygen,  these  gases  would  represent  in  Oxygen  I  73  calories,  equiva- 
lent to  0.0299°  C.  rise,  and  in  Oxygen  II  69  calories,  equivalent  to 
0.0283°  C.  rise. 

In  none  of  the  determinations  referred  to  with  the  above-mentioned 
oxygen  was  more  than  about  45  per  cent  of  these  figures  reached, 
which  can  be  seen  in  Table  IV,  where  the  correction  for  the  impurities 
in  20  atmospheres  ox}Tgen  equals  0.0133°  C.  This  indicates  plainly 
that  only  a  part  of  the  combustible  gases  mixed  with  the  oxygen  can 
be  oxidized  in  the  bomb. 

RISE   IN   TEMPERATURE   CORRECTED   FOR   HEAT   DUE  TO   IMPURITIES    IN   THE   OXYGEN. 

In  Table  VI11  following  are  given  the  corrected  figures  for  the  rise 
in  temperature,  also  the  values  computed  for  the  bomb  water  value  and 
for  the  heats  of  combustion  of  the  substances,  respectively.  The  cor- 
rected figures  for  the  rise  in  temperature  are  obtained  by  using  the 
results  of  Tables  IV  to  VI.  Thus  the  corrections  used  for  the  sugar 
and  cellulose  burned  in  Oxygen  I  are  the  differences  found  in  Tables 
IV  and  V.  No  account  has  been  taken  of  any  increase  in  total  heat 
formed  in  the  bomb  by  use  of  larger  amounts  of  material  with 
Oxygen  I. 

For  the  smaller  charges  of  cellulose  burned  in  Oxygen  II  the  differ- 
ences found  in  Table  VI  have  been  used,  and  for  the  larger  charges 
the  increase  in  rise  of.  temperature  actually  observed  (Table  VII)  has 
been  added  to  the  first-mentioned  correction.  Thus,  where  0.4253  gram 
cellulose  was  burned  in  Oxygen  II  the  correction  will  be  0.00007  X 
24=0.00168°  C.  For  the  charge  of  0.6675  gram  cellulose  the  correc- 
tion will  be  0.00168°+0.0015°  C,  and  for  the  largest  amount  of  cellulose 
burned  the  correction  equals  0.0151°  C. 

To  all  determinations  of  the  other  substances — naphthalene,  cam- 
phor, and  benzoic;  acid — where  the  total  heat  was  a  little  higher  than  it 
was  with  the  cellulose  charge  last  mentioned,  the  same  correction, 
0.0151-  C,  has  been  applied. 

The  heats  of  combustion  were  computed  by  using  the  boml>  water 
value  439.2.  This  value  i-  the  average  of  those  found  for  cellulose, 
naphthalene,  camphor,  and  benzoic  acid  with  Oxygen  II.  The  average 
of  all  the  results  in  Table  VIII  would  be  187.8,  but  the  values  obtained 


FORMATION    OF    NITRIC    ACID. 


27 


with  Oxygen  I  were  not  used  on  account  of  the  sugar  and  cellulose 
not  agreeing  very  closely. 

Table  VIII. —  Water  value  of  the  bomb  calorimeter,  and  heat  value  per  gram  substance, 
worked  out  by  using  the  new  water  vcdue,  439.2,  found  after  applying  the  corrections  for 
the  impurities  in  the  oxygen. 


Substance. 


Stiffar. 


Cellulose 


Cellulose 


Lot  of 

oxygen 

used. 


Naphthalene . 

Camphor 

Benzoic  acid  . 


Oxygen  pres^f"^ 


sub- 
stance. 


Atmospheres. 
10 
.10 
24 
24 
24 
10 
10 
10 
15 
20 
20 
20 
20 
10 
10 
24 
24 
24 
24 
20 
20 
20 
20 
20 
20 


Chroma. 

0.5092 
.5019 
.5054 
.5096 

1.0000 
.3799 
.3840 
.3711 
.3799 
.3800 
.3737 
.3714 
.6800 
.4258 
.4257 
.  4253 
.4276 
.6675 

1.0035 
.5274 
.5430 
.4671 
.5034 
.  6986 
.  7027 


Total  com- 
puted. 


Rise  cor- 
rected for 
oxygen  per 
20  atmos- 
pheres. 


Calories. 
2,050.26 
2,013.96 
2, 038. 32 
2.046.35 
4,106.16 
1,617.47 
1,628.16 
1,571.58 
1,604.70 
1,609.68 
1,584.11 
1,574.21 
2, 868. 06 
1,802.34 
1,803.55 
1,824.37 
1,815.50 
2, 817. 39 
4,229.14 
5, 108. 42 
5, 265. 04 
4, 360. 28 
4, 703. 37 
4,438.67 
4,473.37 


°C. 

0. 8439 

.8307 

.8385 

.8450 

1.7031 

.6605 

.6678 

.6418 

.6578 

.6601 

.6471 

.6425 

1.1834 

.7373 

.7388 

.  7472 

.7433 

1.1548 

1. 7341 

2.0960 

2. 1634 

1.7834 

1.9258 

1.8239 

1.8369 


Bomb 

Calories 

value. 

per  gram. 

429. 5 

3, 969. 7 

424.4 

:?,  976.  4 

430.9 

3,969.0 

421.7 

3, 984. 2 

411.0 

4,001.7 

449. 0 

4,188.9 

438.1 

4,186.9 

448.7 

4, 168. 7 

439. 5 

4,184.8 

438.6 

4, 158. 6 

448.0 

4,170.1 

450.2 

4, 166. 4 

423.6 

4,212.6 

444. 5 

4.17.S.O 

441.2 

4,  LSI.  5 

441.7 

4, 180. 5 

442. 5 

4, 179. 0 

439.7 

4,184.1 

438.8 

4,  IBh.  7 
9, 635. 6 

437. 2 

429. 1 

9,668.3 

444.9 

9, 268. 1 

442.3 

9, 277. 9 

133. 6 

6, 336. 6 

435. 3 

6,332.1 

The  corrected  results  in  Table  VIII  agree  fairly  well  among  them- 
selves, and  even  where  the  conditions  for  determinations  differed  so 
widely  from  the  ordinary  they  approach  the  heat  values  generally 
accepted  for  the  substances  used.  This  certainly  could  not  be  said 
when  the  impurities  were  not  considered,  as  was  seen  in  Table  III, 
where  a  higher  value  was  used  than  the  average  of  the  water  values 
given  in  that  table.  From  all  that  has  been  said  on  this  topic  we  learn 
that,  at  best,  the  determination  of  the  hydrothermo  equivalent,  or 
water  value,  of  the  bomb  with  impure  ox\'gen  is  no  eas}T  task,  nor  can 
it  be  very  satisfactory.  Hence  the  method  explained  can  be  recom- 
mended for  use  only  where  no  pure  oxygen — i.  e. ,  oxygen  free  from 
combustible  gases — can  be  obtained. 


FORMATION   OF   NITRIC   ACID    IN   THE    BOMB   CALORIMETER    DURING 

COMBUSTION. 

The  formation  of  HNOs  in  the  bomb  has  already  been  alluded  to, 
also  that  correction  must  be  made  for  the  heat  represented  by  the 
HN03  solution. 

In  the  bomb  there  is  always  present  more  or  less  free  nitrogen,  and 
a  portion  of  it  is  always  oxidized,  varying  in  quantity  according  to 
the  nature  of  the  substance  burned,  the  total  heat  generated,  and  the 
quantity  of  nitrogen  in  the  bomb.     This  quantity  of  HN03,  which 


28 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


appears  to  be  constant  for  specific  conditions,  1  propose  to  designate, 
for  convenience,  "bomb  nitric  acid,"  meaning  thereby  the  HN03, 
expressed  in  calories,  which  would  be  formed  in  the  bomb  from  free 
nitrogen  during  the  combustion  of  a  specified  substance  under  specified 
conditions.  Table  IX,  following,  gives  us  an  idea  as  to  the  value  of 
this  quantity  for  the  oxygen  used.  This  quantity,  however,  repre- 
sents only  a  ver}7  small  portion  of  the  free  nitrogen  present  in  the 
bomb. 

Table  IX. — Formation  of  HNOtm  the  bovif>  calorimeter  during  combustion  of  nonnitrog- 

enous  substances. 


Substance. 


Cellulose 

Do 

Do 

Sugar 

Do 

Do 

Naphthalene 
Camphor  . . . 
Benzoic  acid 


Determi- 
nations. 


Number. 
6 
7 
6 
4 
7 
2 
2 
2 
2 


Oxygen. 

Weight  of 
substance. 

Total  heat. 

HNOs. 

Atmomkeret. 

Oram*. 

<  'dlorirs. 

Calorics. 

24 

0.5481 

2,335.2 

6.74 

20 

.6650 

2,763.9 

6.50 

10 

.3940 

1, 677.  4 

3.01 

24 

.7538 

3,016.4 

6.13 

20 

1. 2437 

5,019.7 

9.87 

10 

.5056 

2,019.0 

3.20 

20 

.  5352 

5, 182. 2 

8.82 

20 

.4853 

4,531.9 

7.70 

20 

.7007 

4, 454.  6 

7.56 

HNO,  per 

1,000 
calories. 


( 'alorh  8. 
2.89 
2.35 
1.79 
2.04 
1.97 
1.58 
1.70 
1.70 
1.70 


In  the  last  column  of  the  foregoing  table  we  see  that  this  indifferent 
gas  nitrogen  behaves  very  much  like  the  combustible  gases  present  as 
impurities  in  the  oxygen,  namely,  with  an  increase  in  quantity  of 
oxygen,  accompanied  by  an  increase  of  free  nitrogen,  more  nitrogen 
was  oxidized.  The  individual  determinations  also  showed  a  tendency 
to  increased  nitrogen  oxidation  with  an  increase  in  amount  of  sub- 
stance burned. 

For  cellulose  and  the  class  of  substances  which  it  represents,  such 
as  feeds  and  feces,  we  can  use,  without  introducing  any  appreciable 
error  in  the  following  calculations,  a  correction  of  2.4  calories  for 
each  1,000  calories  total  heat  at  20  atmospheres  oxygen  pressure  for 
the  HN03  formed.  For  sugar  and  substances  which  would  burn  more 
like  sugar  than  cellulose,  such  as  gelatin,  dried  urine,  milk,  etc.,  we 
ma}'  use  2  calories  per  1,000  calories  total  heat  as  the  corresponding 
correction  for  the  HN03  formed. 

OXIDATION   OF  COMBINED   NITKOOEN    TO   NITRIC   ACID. 

It  is  generally  assumed  that  the  combined  nitrogen  in  organic  sub- 
stances is  set  free  as  elementary  nitrogen  during  a  combustion.  Hut 
in  view  of  what  has  already  been  said  we  may  be  led  to  question 
u  li<tli»  r  all,  or  at  least  part,  of  this  nitrogen  may  not  also  be  burned 
to  HN03,  perhaps  even  more  readily  BO  than  the  free  nitrogen  gas. 
It  will  be  my  object  to  take  up  the  question  of  nitrogen  of  the  sub- 
stances to  be  analysed,  to  see  how  much  of  this  nitrogen  is  oxidized 
during  a  combustion,  and  what  effect,  if  any,  this  will  have  upon  the 
general  results. 


OXIDATION    OF    COMBINED    NITROGEN    TO    NITRIC    ACID. 


29 


To  illustrate  the  points  which  I  want  to  bring  out  in  this  connection, 
and  to  make  the  tabulated  figures  more  reliable,  I  have  collected  and 
taken  the  average  of  a  large  number  of  figures  from  work  done  at  this 
station  by  Messrs.  Norris  and  Carpenter  on  feeds,  excreta,  etc.,  the 
heats  of  combustion  of  which  were  mostly  used  in  connection  with  the 
nutrition  investigation  experiments  with  cattle  by  means  of  the  respi- 
ration calorimeter,  referred  to  earlier  in  this  paper.  These  data  have 
served  as  the  chief  basis  for  the  computations  set  forth  in  Table  X. 
The  substance  in  each  charge  was  either  a  nitrogenous  compound  or 
mixed  with  one,  so  that  in  each  case  nitrogen  was  present  in  a  com- 
bined form.  From  such  a  variety  of  substances  we  maj^  expect  to  find 
some  differences  brought  out  as  to  the  behavior  in  regard  to  the  nitro- 
gen, if  any  difference  exists. 

Table  X. — Average  HN03  formed  during  the  combustion  of  various   nitrogenous  sub- 
stances in  the  bomb  calorimeter. 


Substance. 


Clover  hay 

Grain  feed 

Corn  meal 

Linseed  meal 

Feces  

Hair  and  dandruff 

Gelatin 

Alcohol+1 

Gelatin     J 

Urine+  \ 

Much  cellulose/"" 
Urine+  1 

Little  cellulose/"" 
Milk+     1 

Cellulose/ 

Milk  alone 


Single 
determi- 
nations. 

Average 
charge. 

Total  heat. 

Nitrogen 
in  charge. 

Bomb 
HNO,. 

Number. 

Grains. 

Calories. 

Grams. 

Calories. 

79 

1.0178 

4,365.8 

.0183 

10.45 

16 

i.oo:si 

4,508.9 

.0342 

10.82 

18 

1.0046 

4,252.9 

.0167 

10. 21 

11 

1. 0110 

4,923.4 

.0616 

11.80 

70 

1.0144 

4,454.3 

.0191 

10.69 

17 

.8218 

3,828.0 

.0601 

7. 66 

5 

.6601 

2,671.4 

.1188 

6.34 

16 

{ 

.6819 
.2006 

4,392.0) 
965.6/ 

.0349 

12.86 

20 

I 

4.7571 

.  8628 

1.182.81 
2,771.7/ 

.0462 

7.91 

29 

! 

7. 5178 
.0508 

1,548.31 
212.8/ 

.0478 

3. 52 

.  9 

! 

1.4648 
.65% 

1,103.91 
2,760.4/ 

.0079 

9.27 

9 

4.0354 

3, 327. 9 

.0225 

6.66 

HNO, 

found. 


Calories. 
5.68 
9.51 
9.38 
13.92 
10.33 
34.10 
12.42 

17.81 

.00 

1.78 

9.22 
9.17 


In  the  above  table  we  find,  besides  the  amount  of  the  sample  used 
and  the  total  heat  produced  in  the  bomb,  the  total  nitrogen  in  the 
charge  taken,  the  bomb  nitric  acid  as  calculated  by  using  the  values 
obtained  in  Table  IX,  and  the  actual  HNOa  found.  It  was  assumed 
that  the  acidity  in  the  bomb  was  due  entirely  to  HN03.  The  figures 
represent  the  averages  of  numerous  closely  agreeing  determinations;  in 
the  case  of  hay,  79  single  determinations.  It  may  be  stated  here  that 
the  nitrogen  represented  by  1  calory  is  equal  to  0.00098  gram,  or  to 
0.004406  gram  HNOs. 

From  these  figures  we  learn  first  of  all  that  the  nitrogen  behaves 
differently  in  different  substances.  Hair  and  dandruff,  for  instance, 
gave  4.5  times  as  much  nitric  acid  as  was  due  to  the  oxidation  of  the 
atmospheric  nitrogen  in  the  bomb,  whereas  gelatin,  which  contained 
about  twice  as  much  total  nitrogen  in  the  sample,  gave  not  much  more 
than  one-third  as  much  nitric  acid  as  did  the  hair  and  dandruff,  and 
only  2.3  times  as  much  as  the  bomb  nitric  acid  called  for.  In  the  case 
of  urine  plus  considerable  cellulose  there  was,  strangely  enough,  no 


30 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


nitric  acid  found  at  all,  yet  about  8  calories  should  have  been  formed 
from  the  free  nitrogen  of  the  bomb  alone.  But  with  urine  plus  a 
little  cellulose  a  small  amount  of  HNOs  was  found.  Naturally,  one 
would  expect  more  where  more  cellulose  was  used.  These  varfations 
may  introduce  errors  into  the  computations  of  the  heat  values  of  the 
substances,  and  in  order  to  see  the  extent  of  these  variations  more 
clearly,  and  perhaps  the  probable  errors,  I  have  presented  the  results 
in  another  form  in  Table  XI. 

Table  XI. — Errors  due  to  the  oxidation  of  nitrogen. 


Substance. 


Clover  hay 

Grain  feed 

Corn  meal 

Linseed  meal 

Feces 

Hair  and  dandruff 

Gelatin 

Alcohol  +gelatin 

Urine + much  cellulose 
Urine+little  cellulose. 

Milk+cellulose 

Milk  alone 


Per  cent 

Nitrogen 

4- Devia- 

found of 

of  sample 

tions  from 

total  HNOj 

oxidized 

bomb 

possible. 

to  HN03. 

HNO3. 

Per  cent. 

Calories. 

19.47 

0.0 

-  4.77 

20.80 

.0 

-  1.31 

31.37 

.0 

-     .83 

18.61 

3.37 

+  2.12 

34.18 

.0 

-     .36 

49.56 

43.02 

+26.44 

9.80 

6.83 

+  7.08 

46.97 

19. 75 

+  4.95 

.0 

.0 

-  7.91 

3.40 

.0 

-  1.74 

5b.  39 

.0 

-     .05 

30.91 

10.91 

+  2.51 

Errors  of 
total  calo- 
ries of 
sample. 


Per  cent. 
0.11 
.03 
.02 
.04 
.01 
.70 
.27 
.11 
.69 
.11 
.00 
.08 


The  bomb  nitric  acid  plus  the  nitric  acid  represented  by  the  oxida- 
tion of  the  total  nitrogen  of  the  charge  is  called  100,  and  in  the  first 
column  of  this  table  are  found,  expressed  in  percentages,  the  amounts 
formed  of  this  possible  HNOs.  In  the  second  column  is  given  the 
percentage  of  the  nitrogen  of  the  sample  oxidized  to  HNO.,.  The  last 
two  columns  give  the  variations  of  nitric  acid  found  from  the  bomb 
HNOj,  a"d  the  percentage  of  the  total  heat  values  represented  by  this 
number  of  calories,  as  calculated  from  the  determinations. 

Several  plus  and  several  minus  deviations  from  the  computed  bomb 
nitric  acid  are  noticed  in  the  preceding  table.  The  minus  signs  force 
us  to  question:  Was  the  full  amount  of  bomb  HN03  not  formed,  or 
was  it  formed  and  did  it  disappear  again,  changed  into  some  other  com- 
pound 1  The  work  done  is  not  enough  to  answer  this  question  fully, 
but  I  am  strongly  inclined  to  believe  that  the  nitric  acid  was  formed, 
but  immediately  on  forming  was  changed  into  some  other  combina- 
tion, probably  through  the  influence  of  the  ash  ingredients. 

In  the  bomb  the  nitric  acid  is  found  dissolved  in  the  moisture  which 
is  condensed  on  the  sides  of  the  bomb.  Here  it  may  be  mentioned 
that  in  transferring  the  nitric  acid  from  the  bomb  to  a  beaker  for 
titration  care  should  be  taken  not  to  wash  out  the  platinum  capsule 
or  add  the  ash  to  the  rinsing.  Often  the  ash  is  very  strongly  alkaline 
and  would  make  the  whole  solution  alkaline,  which  would  be  the  same 
;i-  having  a  minus  quantity  of  acid  formed  -an  impossibility. 

This  finding  of  the  nitric  acid  and  water  together  on  the  sides  of  the 


ERRORS    DUE    TO    VARIOUS    CAUSES.  31 

bomb  would  seem  to  indicate  that  the  nitric  acid  is  formed  as  a  gas, 
and,  together  with  the  water  in  gaseous  form,  is  expelled  or  driven 
from  the  seat  of  the  great  chemical  activity  or  point  of  combustion  to 
unite  and  condense  with  the  moisture  on  the  cool  sides  of  the  bomb. 
But  this  can  not  always  be  the  nature  of  the  combustion,  judging  from 
the  sample  of  urine  plus  considerable  cellulose.  Here  also  the  water  was 
condensed  on  the  sides  of  the  bomb,  and  from  the  cellulose  alone  there 
should  have  been  several  calories  HN03  dissolved  in  it,  but  the  water 
was  neutral.  The  ash,  on  the  other  hand,  was  decidedly  alkaline. 
Where  the  urine  was  burned  with  but  a  small  quantity  of  cellulose 
one-half  of  the  bomb  HNOs  was  found  in  the  water.  Here,  too,  the 
ash  was  alkaline.  Nitric  acid,  it  seems,  can  not  be  formed  by  the 
action  of  the  flame  and  heat  on  nitrogen  away  from  the  ash  or  skeleton 
of  the  substance  burned,  but  must  be  formed  in  the  capsules  holding 
the  substance  at  the  very  point  where  the  heat  first  attacks  the  com- 
pound, the  place  of  greatest  chemical  activity.  We  can  imagine  that 
in  a  remarkably  short  time  numberless  chemical  changes  must  take 
place  at  that  point.  The  nitric  acid  does  not  leave  this  seat  of  action 
when  there  is  some  attraction  strong  enough  to  hold  it.  In  the  case 
of  urine  and  other  substances  such  an  attraction  seems  to  be  in  the  ash, 
and  hence  little  or  none  of  the  nitric  acid  escapes  with  the  other  gases 
formed  to  the  sides  of  the  bomb.  The  attraction  referred  to  can  hardly 
be  anything  but  the  chemical  affinity  of  the  alkalies  of  the  ash,  which 
unite  with  the  acids  formed,  thus  holding  at  least  part  if  not  all  of 
them.  In  this  we  have  an  explanation  of  how  it  is  possible  to  have 
less  than  the  bomb  HN03,  since  ash  with  alkaline  reaction  will  pre- 
vent nitric  acid  from  being  dissolved  in  the  water  and  perchance  pre- 
vent in  part  its  very  formation. 

Eight  ashes  left  by  the  combustion  of  urine  plus  a  little  cellulose 
were  analyzed  for  nitrogen,  and  the  average  of  the  results  gave  the 
equivalent  of  1.1  calory  HNO^,  which  represents  most  of  the  1.74 
calories  of  missing  nitric  acid,  as  shown  in  Table  X.  Unfortunately, 
onty  these  8  ashes  were  saved  for  nitrogen  determination.  What 
the  nitrogen  compounds  were  in  the  ash  was  not  determined,  nor  do 
we  know  anything  about  what  part  of  the  missing  nitric  acid  was 
present  in  the  ash,  in  the  case  of  the  urines,  where  all  was  missing, 
none  being  dissolved  in  the  water  in  the  bomb. 

PROBABLE    ERROR    DUB   TO    DISAPPEARANCE   OF   NITRIC    ACID. 

Taking  for  granted  that  the  plus  values  in  the  table  refer  to  the 
total  nitric  acid  formed,  and  that  not  any  of  it  has  united  with  any- 
thing else,  the  plus  then  does  not  mean  an  error,  since  all  the  nitric 
acid  formed  is  measured  and  accounted  for  in  the  calculations.  But 
the  minus  or  missing  nitric  acid  is  in  all  probability  always  an  error 
which  would  be  greater  or  less  than  the  values  given  in  the  last 
column,  according  to  the  nature  of  the  combination  formed.     Thus 


32 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


errors  are  liable  to  be  introduced  when,  in  the  operation  of  the  bomb 
and  computations  of  the  results,  the  acidity  in  the  solution  titrated 
against  NaOH  solution  is  assumed  to  be  HN03,  and  therefore  the 
amount  of  heat  represented  by  it  always  subtracted  from  the  total 
heat  generated  in  the  bomb. 

There  are  other  acids  formed  in  the  bomb  besides  nitric  acid,  and 
directions  for  the  manipulation  of  the  bomb  calorimeter  should  make 
specific  mention  of  this.fact  and  explain  how  they  should  be  considered}, 
so  as  not  to  introduce  sa\y  error.  They  are  not  in  any  way  equivalent 
to  HN03,  and  should  therefore  not  be  treated  as  such.  The  writer 
has  in  mind  especially  the  H2S04. 

It  is  generally  accepted  that  in  a  complete  combustion  of  a  nitrog- 
enous organic  substance  the  nitrogen  returns  to  free  nitrogen  and 
oxidizes  only  under  extraordinary  conditions  such  as  may  be  produced 
by  a  powerful  electric  spark,  or  which  exists  in  the  bomb  calorimeter 
where  the  combustion  takes  place  in  the  presence  of  large  excess  of 
oxygen,  etc.  For  this  reason  any  heat  caused  by  the  formation  of 
HNO3  must  be  subtracted  from  the  total  heat  generated  in  the  bomb. 

With  sulphur  compounds  it  is  different.  The  natural  combustion 
product  of  sulphur  is  the  acid,  and  hence  any  heat  produced  by  the 
formation  of  H2S04  belongs  to  the  compound  and  should  not  be  sub- 
tracted. Especially  is  this  true  when  the  bomb  results  are  to  be  com- 
pared with  the  combustions  of  organic  substances  as  they  take  place  in 
the  animal  body.  Part  or  all  of  the  sulphuric  acid  may  be  held  in  the 
form  of  salts  in  the  ash,  but  as  the  ash  is  practically  an  unexplored 
field,  it  will  not  be  touched  upon  at  all  at  this  time. 

Whether  the  H2S04  is  counted  in  as  HN03  or  not  will  at  times  make 
a  great  difference  in  the  final  results.  This  may  be  seen  very  clearly 
from  some  work  which  the  writer  did  upon  dandruff  and  hair  (brushed 
off  a  steer  at  the  daily  cleaning),  upon  pure  hair,  and  upon  two  sam- 
ples of  steer  urine. 

The  results  so  far  as  they  bear  upon  this  point  are  found  in  Table  XII. 

Tablk  XII. — Difference  in  the  he* it  values  found  when  the  total  acidity  is  regarded  eu 
IfNOi  and  when  the  II.ISOt  has  been  subtracted. 


Charge. 

Acid  solution  titrated  against 
NaOH  solution. 

Calories  per  gram  sub- 
stance. 

Differ- 
ence. 

Bntautce. 

Total 
alkali. 

Due  to 
Hj,S04. 

Differ- 
ence 
II  No,. 

Acidity 

called 
HNO  . 

Titration 
corrected 
for  M,.S()4. 

Brushing*   (dandruff  mid 
hair)  

drams. 
1.0236 

.8808 

7.9402 
ti  1216 
6.0444 
7.6021 
7.8184 

V  HIT 

<■.  r. 

69.79 
69. 62 
49.94 
1.80 
l .  86 
1.82 
2.92 
:;  18 
8.86 

c.  c. 
62. 9K 
6H.KS 
6K.27 
88  54 

1         l'] 

|          3.1 

Citlm-ii*. 

1.36 

II    10 

3.  '.17 

4,062.4 
4,048.7 
L  066.6 
6,180.8 

l  ,::  M 
176.6 

1,118.8 
1.  126.7 

4,132.7 
6,221.4 

163.42 
176.73 

fi  r  cent 
1.48 

Do 

1.87 

Do  

1.60 

Bail 

.79 

Trim • 

Do 

.04 

Do 

Do     

Do 

.07 

Do 

CAUSE  OF  INCOMPLETE  COMBUSTION.  83 

These  few  determinations  will  suffice  to  show  that  a  very  large  error 
may  be  introduced  by  the  H2S04.  In  the  case  of  urine  the  error  intro- 
duced by  reckoning  sulphuric  acid  as  nitric  acid  is  small,  but  with  the 
hair  it  reached  about  0.8  per  cent,  and  in  the  case  of  the  epidermic 
tissue,  dandruff,  etc.,  which  is  richer  in  sulphur,  the  error  was  in  one 
instance  about  1.9  per  cent. 

CAUSE  OF  INCOMPLETE  COMBUSTION. 

The  shape  and  size  of  crucible,  or  capsule,  in  which  the  substance  is 
burned  may  influence  the  combustion. 

Owing  to  inability  to  watch  the  process  of  the  combustion  in  the 
bomb,  the  general  opinion,  gained  perhaps  from  the  observations  of 
explosives,  is  that  the  combustion  in  the  bomb  calorimeter  is  veiy 
sudden  and  violent,  in  nature  like  an  explosion  in  the  free  air.  This, 
however,  is  not  correct.  The  time  of  combustion  varies  with  the 
nature  of  the  substance,  but,  with  the  materials  mentioned  in  the 
previous  tables,  onl}T  by  a  very  few  seconds.  It  is  of  a  very  short 
duration,  but  by  no  means  an  instantaneous  flash.  The  supposed  vio- 
lence, implying  that  the  flash  fills  the  bomb,  has  absolutely  no 
foundation  and  would  not  happen  except  when  the  oxygen  contains  a 
considerable  percentage  of  highby  combustible  gases.  To  prove  the 
correctness  of  this  statement  direct  tests  were  made  as  follows:  Small 
pieces  of  filter  paper,  about  one-fourth  inch  square,,  were  fastened  bjr 
one  edge  to  the  sides,  top,  and  bottom  of  the  bomb  by  means  of  paste, 
and  allowed  to  dry.  In  one  trial  the  burning  of  a  small  charge  of 
cellulose  did  not  affect  the  few  pieces  of  filter  paper  which  were 
fastened  on  the  top  and  on  the  bottom  of  the  bomb.  After  that  a  more 
complete  test  was  made  by  fastening  three  pieces  to  the  top,  one  at 
the  center  of  the  bottom,  and  ten  distributed  on  the  sides  of  the  bomb; 
four  of  them  about  opposite  the  top  of  the  capsule,  four  nearer  the 
top,  and  two  nearer  the  bottom.  The  charge  was  1  gram  powdered 
rock  candy  plus  a  little  naphthalene,  burned  in  20  atmospheres  oxy- 
gen. The  test  resulted  in  two  of  the  three  pieces  on  the  top  being 
burned,  the  third  one  showing  in  one  corner  a  trace  of  brown  as  when 
paper  has  been  held  near  strong  heat.  All  the  rest  were  absolutely 
untouched.  Hence,  the  flames  may  at  times  reach  the  top,  and  per- 
haps more  seldom  the  sides,  though  the  distance  is  much  shorter. 
With  more  oxygen  the  flame  very  likely  would  not  even  have  reached 
the  top  of  the  bomb. 

It  is  a  known  fact  that  fire  will  put  itself  out  in  a  closed  room,  even 
before  the  oxygen  is  fully  consumed.  If  this  is  true  in  a  room,  might 
it  not  also  be  true  in  a  deep  capsule  surrounded  by  plent\T  of  oxygen? 
To  have  some  light  shed  upon  this  question,  and  to  be  able  to  decide 
in  favor  of  some  one  of  the  different  shaped  capsules  used,  the  follow- 


34 


INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 


ing  tests  were  made:  A  wide-mouthed  bottle  of  1,500  c.  c.  capacity 
was  filled  with  oxygen,  and  the  crucible,  attached  to  a  wire  fastened 
in  the  cork,  was  let  down  in  the  bottle,  and  the  substance  ignited  by 
means  of  an  iron  fuse  wire  as  in  the  case  of  the  bomb  combustion,  and 
the  burning  watched.  The  substances  burned  were  filter  paper  (cellu- 
lose), cut  in  disks  and  laid  on  the  bottom  of  the  crucible,  and  powdered 
sugar  (rock  candy).  After  combustion  the  ordinary  test  was  made 
for  the  oxygen  by  means  of  a  glowing  splinter  of  wood.  In  all  cases 
there  was  a  large  excess  of  oxygen,  since  the  large  cork  could  be 
removed  and  the  splinter  plunged  in  and  ignited  several  times  in  suc- 
cession. 

In  the  following  table,  which  gives  the  results  of  the  tests,  crucible 
No.  1  was  a  large  nickel  crucible,  If  inches  in  diameter  at  the  top  and 
IjV  inches  deep.  Crucible  No.  2  was  a  small  nickel  crucible,  i  inch  in 
diameter  by  { ^-inch  deep.  Crucible  No.  3  was  the  same  as  No.  2,  per- 
forated, and  crucible  No.  4  was  the  same  as  No.  3  with  the  holes 
enlarged.  A  small  piece  of  cellulose,  not  weighed,  was  put  under  the 
sugar  in  the  crucible  in  one  case  to  facilitate  the  combustion.  The 
time  which  the  substance  stood  in  the  bottle  before  ignition  was  noted, 
as  well  as  the  length  of  time  it  continued  to  burn.  The  last  column 
in  the  following  table  gives  the  unburned  residue: 

Tajlk  Xllt. — Powdered  sugar  and  cellulose  burned  in  different  shaped  crucibles  in  oxijgen 

under  atmospheric  pressure. 


Substanee. 


Cellulose 

Sugar 

Do 

Cellulose 

Sugiir 

Do 

Sugar  and  cellulose 
Cellulose 


Cruci- 
ble. 

Weight  of 
substance. 

Time  be- 
fore igni- 
tion. 

Time  of 
combus- 
tion. 

drum. 

Minute*. 

Seconds, 

1 

0.2190 

30 

60 

1 

.2675 

5 

75 

2 

.  2154 

5 

180 

2 

.1X90 

5 

165 

3 

.2582 

8 

195 

4 

.2132 

90 

75 

4 

.2037 

5 

60 

4 

.1585 

15 

40 

Unburned 

residue. 


Oram. 

0.0000 
.0077 
.0081 

.  oasts 

.0122 
.  1609 
.0060 
.0002 


In  only  one  instance  did  the  substance  burn  without  leaving  any 
unburned  residue  of  carbon.  There  was  a  marked  difference  between 
the  two  substances  in  the  way  they  burned,  the  sugar  taking  longer 
time  and  leaving  a  great  deal  of  unburned  matter.  A  number  of  holes 
were  made  near  the  bottom  of  the  small  crucible.  During  the  burning 
some  of  the  holes  became  coated  over  with  a  film  of  charred  material, 
the  flame  remained  smaller,  and  the  circulation  of  the  gases,  i.  e.,  of 
oxygen,  to  the  burning  substance  was  lessened.  When  the  holes  were 
enlarged  these  last-mentioned  hindrances  were  magnified  and  the  sugar 
burned  only  in  part,  most  of  it  was  left  untouched  by  tli«'  small  flame, 
and  in  one  spot  it  was  not  even  fully  melted.  It  is  possible  that  in  this 
ease  some  of  the  oxygen  might  have  leaked  out  on  standing.  but  after 


ALCOHOL    HEAT    VALUE.  35 

the  combustion  there  was  enough  left  in  the  bottle  to  allow  the  glowing- 
splinter  to  burst  into  flame  several  times.  When  the  sugar  rested  on 
a  small  piece  of  filter  paper  the  combustion  of  the  sugar  was  more 
nearly  complete,  and  filter  paper  alone  was  practically  completely 
burned  in  crucible  No.  4. 

The  figures  of  the  table,  as  well  as  the  actual  behavior  of  the  com- 
bustion, indicate  the  shape  of  the  larger  crucible,  which  was  very 
much  broader  at  the  top  than  at  the  bottom,  as  being  the  best.  The 
combustion  itself,  or  we  may  say  the  supply  of  oxygen  to  the  burning 
points,  was  more  uniform  with  the  larger  and  more  intermittent  with 
the  smaller  crucible.  A  good  start,  and  much  heat  quickly  generated, 
are  factors  which  undoubtedly  contribute  much  to  make  a  combustion 
complete,  but  these  may  not  in  the  least  change  the  conclusion  reached 
as  to  the  shape  of  the  crucible  or  capsule  best  suited  for  the  work. 

ALCOHOL  HEAT  VALUE. 

Time  did  not  permit  me  to  take  up  the  question  of  alcohol  heat 
value  as  fully  as  I  desired,  hence  at  this  time  I  shall  make  mention  of 
only  a  few  points  which  have  come  up  in  connection  with  the  determi- 
nation of  heat  of  combustion,  and  make  some  suggestions  which  ma}r 
at  least  be  of  practical  value. 

Alcohol  being  a  volatile  liquid  it  can  not  be  satisfactorily  burned  in 
an  open  dish,  but  must  be  inclosed  in  a  receptacle  from  which  it  can 
not  evaporate,  and  gelatin  capsules  of  known  heat  value  are  generally 
used  for  this  purpose.  The  alcohol  charge  should  never  be  weighed 
out  by  difference — i.  e.,  by  weighing  the  bottle — but  the  actual  amount 
placed  in  the  capsule  should  be  weighed.  The  reason  for  this  is  to 
make  sure  that  there  is  no  evaporation.  Unless  the  capsule  with  the 
alcohol  is  weighed  a  little  evaporation  may  not  be  noticed,  and  if  the 
capsule  is  not  tight  enough  to  hold  the  alcohol  while  it  is  being 
weighed  it  is  not  fit  for  the  work.  A  little  evaporation  of  alcohol 
from  the  capsule  in  the  bomb  will  alwajs  cause  the  results  to  come  too 
low,  since  alcohol  vapors  are  not  full}7  burned.  To  insure  complete 
combustion  of  the  alcohol  and  the  gelatin  the  capsule  may  be  filled 
with  clean,  ignited  asbestos  to  absorb  the  alcohol. 

Another  way  to  obtain  good  combustions  of  the  alcohol  and  gelatin, 
though  not  so  simple  as  the  gelatin-capsule  method,  is  to  make  use  of 
a  tubular  platinum  capsule,  about  one-fourth  of  an  inch  in  diameter, 
having  perforated  sides  and  bottom.  This  platinum  capsule  is  coated 
with  a  mixture  of  the  best  gelatin  with  about  10  per  cent  of  glycerin 
and  water,  all  gently  heated.  The  coating  is  allowed  to  dry,  and  the 
weight  of  the  gelatin  mixture  is  ascertained.  Separate  portions  of  the 
mixture  are  dried  and  analyzed  for  the  heat  value.  This  gelatin- 
coated  capsule  can  be  used  with  or  without  asbestos.  Caps  can  be 
made  of  the  same  material  to  tit  tightly  over  the  end,  or  inverted,  used 


36 


INVESTIGATIONS   IN    USE    OF    BOMB    CALORIMETER. 


as  plugs.     It  requires  less  gelatin  to  coat  such  a  capsule  and  make  it 
alcohol  tight  than  is  found  in  the  ordinary  gelatin  capsules  used. 

The  weight  of  all  gelatin  capsules,  etc.,  should  be  taken  when  the 
the  material  is  dr}%  and  this  weight  should  be  used  in  correcting  for 
the  heat  of  combustion  of  gelatin.  But  before  using  they  should  have 
been  exposed  to  room  conditions  for  a  considerable  time,  else  there  is 
no  constancy  about  them  when  they  have  to  be  reweighed  and  filled 
with  alcohol. 

ALCOHOL   DETERMINATION    USED   FOR   TESTING  THE    RESPIRA- 
TION CALORIMETER. 

This  was  absolute  alcohol  diluted  with  distilled  water,  and  hence  the 
first  step  was  to  obtain  its  specific  gravity.  Two  p}Tcnometers  were 
used  and  the  specific  gravity  was  taken  at  15.6°  C,  as  follows: 


No.  1. 

No.  2. 

GrawiS. 
77.2663 
27.2386 

Grams. 
87. 2591 

37. 2269 

50. 0278 
.05894 

50.0332 
.05894 

Water 

50.08674 

50.09214 

68.  4121 
27.2385 

78.4056 

37. 2259 

JiO  c<\  air 

41.1736 
.05894 

41.1797 
05894 

Alcohol '. 

41.23254 

41.23864 

No.  1.  41.23254--50.08674=. 823222  specific  gravity. 
No.  2.  41.23864--50.09214=.823255  specific  gravity. 

Average,  =.823238  specific  gravity. 

According  to  Squibb,  at  15.6°  C. 

0.82755  specific  gravity =88.0  per  cent  pure  alcohol. 
.81684  specific  gravity=92.0  per  cent  pore  alcohol. 


Differenci', 


.01071  specific  gravity=  4.0  per  cent  pure  alcohol. 
0.82755  =88.0  per  cent  alcohol. 
.823238=  unknown  alcohol. 


.004312 
0.01071  :  0.004312  ::4.0  :X 


X  =  1.6105  per  cent. 


Hence  88.0    1.<>105=89.<>1 1  per  pent  ethyl  alcohol 

DETERMINATION  OF  HEAT   OF   COMBUSTION. 

Using  the  old  water  value  of  the  bomb  and  without  any  correction 
for  oxygen,  two  determinations  of  the  capsule  gelatin  gave  an  aver- 
age of  4,N71  calories  per  gram,  and  the  average  of  three  determina- 
tion- of  the  alcohol  gave  6,458.7  calories  per  grain,  or  7,207  calories 
per  gram  pure  alcohol.  Applying  the  correction  found  for  impurities 
in  oxygen  by  burning  1  gram  cfeJIttlose,  and  using  the  corresponding 
water  value  of  the  bomb,  the  average  for  the  gelatin  was  4,860  calo- 


DETERMINATION    OF    HEAT    OF    COMBUSTION.  37 

ries  per  gram,  and  for  the  alcohol  6,447  calories  per  gram,  or  7,194 
calories  per  gram  pure  alcohol. 

A  sudden  jar  of  the  bomb  caused  one  capsule  containing  alcohol  to 
fall  to  the  bottom  of  the  bomb.  It  was  ignited,  and  the  determina- 
tion was  carried  through  as  usual,  but  only  6,949.8  calories  per  gram 
pure  alcohol  was  measured. — that  is,  3.4  per  cent  less  than  the  above 
average.  Upon  opening  the  bomb  there  was  found  a  black  spot  and 
some  3^ellowish  oily  liquid  at  the  bottom,  and  a  strong,  verj-  peculiar 
odor  mixed  with  odor  of  alcohol  was  noticed,  thus  showing  incomplete 
combustion  very  decidedly.  Another  charge  of  alcohol  which  had 
remained  in  the  capsule  in  the  bomb  for  several  hours  before  ignition 
gave  7,091  calories  per  gram  pure  alcohol.  Here,  where  there  was 
opportunity  for  evaporation,  the  heat  obtained  was  less  than  the  aver- 
age of  the  three  other  determinations. 

These  observations  are  sufficient  to  show  that  to  obtain  correct 
values  great  care  must  be  taken  when  volatile  substances  are  to  be 
burned  in  the  bomb. 

One  or  two  questions  which  may  possibly  prove  to  be  of  some  im- 
portance in  connection  with  this  work  will  be  considered  briefly. 

These  questions  concern  the  contents  of  the  bomb  before  and  after 
combustion,  and  their  influence  upon  the  measurement  of  the  heat, 
namely,  the  influence  which  the  changes  in  the  contents  have  upon  the 
water  value  of  the  bomb,  and  the  quantity  of  heat  held  b}r  these  vari- 
ous compounds  formed  and  not  accounted  for. 

In  the  following  calculations  I  shall  use  the  values  for  specific  heats, 
etc.,  as  given  belowr: 

Per  unit  weight: 

Cane  sugar=0.  301  specific  heat. 
Water  =1.  000  specific  heat. 
02  =  .2175  specific  heat. 

C02  =  .  1875  specific  heat. 

02  1  liter    =1.4298  gram. 

To  illustrate  these  problems  and  for  the  sake  of  simplicity  we  shafl 
consider  one  example,  leaving  out  all  of  the  minor  things  which  would 
complicate  the  calculations.  Thus,  we  have  a  bomb  of  360  c.  c.  capacity. 
In  the  bomb,  before  combustion,  are  1  gram  cane  sugar  and  20  atmos- 
pheres pure  oxygen,  all  at  20°  C.  What  changes  take  place  when  the 
sugar  is  burned,  and  what  are  their  significance? 

According  to  the  weight  and  specific  heat  of  the  substances  in  the 
bomb,  they  represent  a  certain  mass  of  water  at  the  same  tempera- 
ture; also,  a  definite  quantity  of  heat  is  held  by  them,  which  may  be 
expressed  in  calories.     Twenty  atmospheres  oxygen  would  then  be — 

20X360  c.  c.  =7,200  c.  c.  oxygen. 

7,200X1.4298  (weight  of  1  liter  oxygen) =10.29456  grams  oxygen. 

10.29456X0.2175  (specific  heat)<>2.239  grams  water. 

1  gram  cane  sugar  X0.301  specific  heat<>0.301  gram  water.  ■ 


38  INVESTIGATIONS    IN    USE    OF    BOMB    CALORIMETER. 

Hence  the  substances  in  the  bomb  represent — 

Oxygen  2. 239  grams  H20 

Sugar  .  301  grams  H20 

Total     2.  540  grams  H20 

The  sugar  burns  to  C02  and  H20,  and  after  the  combustion  of  1 
gram  sugar  we  find  0.5793  gram  water  and  1.5426  gram  COr 

1.5426  grams  CO2x0.1870  specific  heat=0.288  gram  water. 
10.29456—1.1219=9.1727  grams  02,  and  X0.2175=1.933  grams  water. 

Thus  in  the  bomb  after  combustion  we  have — 

Oxygen  equivalent  to  1.  933    grams  H20 

Carbon  dioxide  equivalent  to  .  288    gram  H20 

Water  .  5793  gram  H20 

Total  .  2. 8003  grams  H20 

After  combustion  2.  8003  grams  water 

Before  combustion  „  2. 5400  grams  water 


Difference  (increase)  .2603  gram  water 

The  whole  bomb  system  therefore  has  changed  to  an  extent  equiva- 
lent to  0.2603  gram  water  during  the  combustion.  This  is  equal  to 
0.011  per  cent  of  the  total  bomb  water  value  plus  water  used,  or  an 
error  of  about  one-half  calory  in  the  ordinary  determination.  If,  for 
instance,  1  gram  butyl  alcohol  should  be  burned  instead  of  sugar,  the 
change  in  the  system  would  be  equal  to  0.1685  gram  water — an  error 
of  0.019  per  cent. 

This  is  a  very  small  error,  and,  at  the  present,  is  perhaps  altogether 
negligible. 

The  next  question  is,  To  what  extent  does  this  change  of  contents 
affect  the  heat  evolved  during  the  combustion? 

This  question  refers  to  the  same  changes  in  the  contents  of  the  bomb 
as  did  the  preceding  one,  but  instead  of  studying  their  effect  upon  the 
water  value  of  the  bomb  we  want  to  see  what  the  effect  will  be  upon 
the  determination  of  heat  of  combustion  when  the  factor  for  the  bomb 
and  the  water  used  remains  the  same. 

In  the  case  of  the  sugar  there  was  an  increase  of  0.2603  gram  water 
in  the  bomb,  which,  raised  to  1.7°  C,  would  equal  about  one-half  calory 
held  by  it.  The  correction  will,  in  other  words,  in  the  case  of  sugar, 
be  the  Bame  whichever  way  we  apply  it,  but  this  is  not  necessarily  true 
of  all  substances  burned.  As  said  before,  the  correction  is  so  small 
that  it  need  seldom  be  considered. 

CONCLUSION. 

From  what  has  been  said,  thru,  we  learn  that  there  are  many  possi- 
bilities for  error  in  the  work  with  the  bomb  calorimeter.  Undoubtedly 
m:in\   investigators  in  the   past    have  worked  with  impure  oxygen  and 


CONCLUSION.  39 

never  questioned  its  purity.  In  the  light  of  our  present  experience  it 
is  questionable  whether  Stohmann  himself,  by  the  use  of  a  heated 
copper  tube,  could  have  removed  the  last  traces  of  combustible  gases 
from  his  oxygen. 

The  disappearance  of  nitric  acid  formed  and  its  relation  to  the  ash 
has  not  been  taken  into  consideration,  and  it  is  only  within  a  couple 
of  years  that  the  thermometer  lag  has  come  to  be  applied  in  the  calcu- 
lations of  the  results. 

These  overlooked  or  at  times  unknown  difficulties,  which  have  been 
referred  to  throughout  this  paper,  may  be  the  cause  of  some  of  the 
disagreements  of  results  as  experienced  by  different  investigators  and 
referred  to  in  the  earlier  part  of  this  paper. 

From  what  has  been  done  and  said  I  believe  we  also  have  learned 
that  much  work  is  yet  needed  in  the  different  lines  indicated  before 
the  method  for  determinations  of  heat  of  combustion  by  means  of  the 
bomb  calorimeter  can  be  called  perfect. 


o 


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